Hello,
I don't know if this one as already been reported :

When editing the global 'paramIconSize' in globals parameters view, and if a user has already set his own value, the new global parameter will not be saved.
Instead, the parameter is saved as a new one in database with a NULL 'parameterCode' value.
After a little modification in 'saveParameter.php' (tool/saveParameter.php), the parameter is now properly saved.

Before : (line 141)

      $crit['parameterCode']=$fld;
      $obj=SqlElement::getSingleSqlElementFromCriteria('Parameter', $crit);

After :

      $crit['parameterCode']=$fld;
      $crit['idUser']=null;
      $crit['idProject']=null;
      $obj=SqlElement::getSingleSqlElementFromCriteria('Parameter', $crit);

As the global parameter and user parameter has the same 'parameterCode', the 'getSingleElementFromCriteria()' method can't retrieve a unique result.

By the way, thanks for your great work on this project, it's awesome.