Any error in Browser console ?
Did you try and clean browser cache ?

Cache cleared.
IE & Forefox

Console log in firefox:

"=> 129ms | page='../tool/loginCheck.php' | destination='loginResultDiv' | formName=loginForm' (server:113ms, client:16ms)" projeqtor.js:75:2
ReferenceError: assignment to undeclared variable resultNode projeqtor.js:743:13
ReferenceError: assignment to undeclared variable resultWidget projeqtor.js:744:15
ReferenceError: assignment to undeclared variable url projeqtor.js:755:6
Object { message: "Unable to load ../tool/saveDataToSe…", stack: ".cache["dojo/errors/create"]/</</_4…", response: Object, status: 0, responseText: "", xhr: XMLHttpRequest } dojo.js:15:102024
.cache["dojo/_base/xhr"]/</_3c4() dojo.js:15
.cache["dojo/_base/xhr"]/</dojo._ioSetArgs/<() dojo.js:15
_189() dojo.js:15
_187() dojo.js:15
.cache["dojo/_base/Deferred"]/</dojo.Deferred/this.errback() dojo.js:15
_189() dojo.js:15
_187() dojo.js:15
.cache["dojo/_base/Deferred"]/</dojo.Deferred/this.errback() dojo.js:15
_189() dojo.js:15
_187() dojo.js:15
.cache["dojo/_base/Deferred"]/</dojo.Deferred/this.errback() dojo.js:15
.cache["dojo/_base/xhr"]/</dojo.xhr/<() dojo.js:15
.cache["dojo/Deferred"]/</_3e7() dojo.js:15
.cache["dojo/Deferred"]/</_3e1() dojo.js:15
.cache["dojo/Deferred"]/</_3e6/this.reject() dojo.js:15
.cache["dojo/Deferred"]/</_3ed() dojo.js:15
.cache["dojo/Deferred"]/</_3e7() dojo.js:15
.cache["dojo/Deferred"]/</_3e1() dojo.js:15
.cache["dojo/Deferred"]/</_3e6/this.reject() dojo.js:15
.cache["dojo/Deferred"]/</_3ed() dojo.js:15
.cache["dojo/Deferred"]/</_3e7() dojo.js:15
.cache["dojo/Deferred"]/</_3e1() dojo.js:15
.cache["dojo/Deferred"]/</_3e6/this.reject() dojo.js:15
.cache["dojo/Deferred"]/</_3ed() dojo.js:15
.cache["dojo/Deferred"]/</_3e7() dojo.js:15
.cache["dojo/Deferred"]/</_3e1() dojo.js:15
.cache["dojo/Deferred"]/</_3e6/this.reject() dojo.js:15
.cache["dojo/Deferred"]/</_3ed() dojo.js:15
.cache["dojo/Deferred"]/</_3e7() dojo.js:15
.cache["dojo/Deferred"]/</_3e1() dojo.js:15
.cache["dojo/Deferred"]/</_3e6/this.reject() dojo.js:15
_31b() dojo.js:15
_328() dojo.js:15

Object { message: "Unable to load ../tool/saveDataToSe…", stack: ".cache["dojo/errors/create"]/</</_4…", response: Object, status: 0, responseText: "", xhr: XMLHttpRequest } dojo.js:15:102024

TypeError: variable year redeclares argument projeqtor.js:2312:7
TypeError: variable text redeclares argument projeqtor.js:2469:5
ReferenceError: assignment to undeclared variable avoidRecursiveRefresh projeqtor.js:238:0
...

What is strange is the line

Object { message: "Unable to load ../tool/saveDataToSe…", stack: ".cache["dojo/errors/create"]/</</_4…", response: Object, status: 0, responseText: "", xhr: XMLHttpRequest } dojo.js:15:102024

It seems saveDataToSession.php fails.
Maybe you have cookie issue (retreiving session from old connection with previous version).
First, try and delete cookies linked to projeqtor calls.

If this does not fix issue, in dev tools [F12], open network tab and look for request to saveDataToSession.php.
Post request and response, it may give some hints.

Thx for your reply.
I deleted cookies.

Here are two videos to explain what is happening.
There are not a lot of info when tracing of saveDataToSession.php (the second video), only the headers.
What do you like more?

Video 1: www.ceria.be/projeqtor/001.avi
Video 2: www.ceria.be/projeqtor/002.avi

Hi,

So I see in Video 1 that you are connected correctly, but immediatly disconnected.
It is strange 'cos your get this directly when getting main page : you directly have "?lostConnection=true" in the url.

So I see two possibiities :
1) you changes somthing is the parametering that sets login page as default page
Check all lines in parameters table where parameterCode='startPage'
2) there is some parameter in config that the application interprets as some acking attempt.
Then, you should have at least a trace in the log file.
Try and set debug level to 4 and post log file here.

The value of startPage is startGuide.php
In my 4.5.6, the value is today.php

Log in Firefox

2015-10-20 09:15:55.905 ..... SCRIPT .... 10.200.200.106 /tool/getHash.php
2015-10-20 09:15:55.921 ..... SCRIPT .... 10.200.200.106 Page=getHash.php
2015-10-20 09:15:55.968 ..... SCRIPT .... 10.200.200.106 /tool/loginCheck.php
2015-10-20 09:15:55.968 ..... SCRIPT .... 10.200.200.106 Page=loginCheck.php
2015-10-20 09:15:55.968 ..... SCRIPT .... 10.200.200.106    ->/tool/loginCheck.php
2015-10-20 09:15:56.061 ===== TRACE ===== NEW CONNECTED USER 'admin'
2015-10-20 09:15:56.124 ..... SCRIPT .... 10.200.200.106 /view/main.php
2015-10-20 09:15:56.124 ..... SCRIPT .... 10.200.200.106 Page=main.php
2015-10-20 09:15:56.202 ..... SCRIPT .... 10.200.200.106    ->/view/main.php
2015-10-20 09:15:56.358 ..... SCRIPT .... 10.200.200.106    ->/view/menuTree.php
2015-10-20 09:15:56.498 ..... SCRIPT .... 10.200.200.106    ->/view/menuBar.php
2015-10-20 09:15:56.514 ..... SCRIPT .... 10.200.200.106 Project(*)->drawSubProjects(selectField=selectedProject, recursiveCall=, limitToUserProjects=1, limitToActiveProjects=1)
2015-10-20 09:16:01.288 ..... SCRIPT .... 10.200.200.106 /tool/jsonDirectory.php
2015-10-20 09:16:01.288 ..... SCRIPT .... 10.200.200.106 Page=jsonDirectory.php
2015-10-20 09:16:01.381 ..... SCRIPT .... 10.200.200.106    ->/tool/jsonList.php
2015-10-20 09:16:01.459 ..... SCRIPT .... 10.200.200.106 /tool/saveDataToSession.php
2015-10-20 09:16:01.459 ..... SCRIPT .... 10.200.200.106 Page=saveDataToSession.php
2015-10-20 09:16:01.490 ..... SCRIPT .... 10.200.200.106 /tool/saveDataToSession.php
2015-10-20 09:16:01.490 ..... SCRIPT .... 10.200.200.106 Page=saveDataToSession.php
2015-10-20 09:16:01.522 ..... SCRIPT .... 10.200.200.106 /tool/saveDataToSession.php
2015-10-20 09:16:01.522 ..... SCRIPT .... 10.200.200.106 Page=saveDataToSession.php
2015-10-20 09:16:01.537 ..... SCRIPT .... 10.200.200.106 /tool/saveDataToSession.php
2015-10-20 09:16:01.537 ..... SCRIPT .... 10.200.200.106 Page=saveDataToSession.php
2015-10-20 09:16:01.568 ..... SCRIPT .... 10.200.200.106 /tool/saveDataToSession.php
2015-10-20 09:16:01.568 ..... SCRIPT .... 10.200.200.106 Page=saveDataToSession.php
2015-10-20 09:16:01.600 ..... SCRIPT .... 10.200.200.106 /tool/saveDataToSession.php
2015-10-20 09:16:01.600 ..... SCRIPT .... 10.200.200.106 Page=saveDataToSession.php
2015-10-20 09:16:01.631 ..... SCRIPT .... 10.200.200.106 /tool/cronRelaunch.php
2015-10-20 09:16:01.631 ..... SCRIPT .... 10.200.200.106 Page=cronRelaunch.php
2015-10-20 09:16:01.662 ..... SCRIPT .... 10.200.200.106 /view/startGuide.php
2015-10-20 09:16:01.662 ..... SCRIPT .... 10.200.200.106 Page=startGuide.php
2015-10-20 09:16:01.662 ..... SCRIPT .... 10.200.200.106    ->/view/login.php
2015-10-20 09:16:01.958 ..... SCRIPT .... 10.200.200.106 /view/main.php
2015-10-20 09:16:01.958 ..... SCRIPT .... 10.200.200.106 Page=main.php
2015-10-20 09:16:02.068 ..... SCRIPT .... 10.200.200.106    ->/view/main.php
2015-10-20 09:16:02.208 ..... SCRIPT .... 10.200.200.106    ->/view/menuTree.php
2015-10-20 09:16:02.348 ..... SCRIPT .... 10.200.200.106    ->/view/menuBar.php
2015-10-20 09:16:02.364 ..... SCRIPT .... 10.200.200.106 Project(*)->drawSubProjects(selectField=selectedProject, recursiveCall=, limitToUserProjects=1, limitToActiveProjects=1)

Log file is here

Could you please post "ProjeQtOr" log file.

Thre is really no issue in the log file.
It is very, very strange.

Could you try :
1) change startPage to "today.php" (to be sure it is not a side effect)
2) disable all extensions and plugIns from browser (some plugins such as Skype click to call are know to set a mess)
3) check Apache error log file and access log file

Sorry for the late reply, a lot of work and vacation :cheer:
I think I found. With my PHP, I use php_opcache.dll
If I disable the opcache in my VHOST (php_value opcache.enable off), it seems to work.
I will test some more

I migrated my version 4 in the latest version 5.1.1 and everything seems to work.

I consider my problem solved.
A big thank you for the follow.