Now Microsoft suprised us (again): with the last update of Visual Studio 2012 (this is the software for developing ProfiLuxControl) the Windows XP-support has been removed!
It seems Microsoft is already terminating the XP-support.

Result: The current PLC 5.1.6.0 runs only on Vista or higher.

-> if you still use XP you should stay at 5.1.5.4 for the moment

we hope that Microsoft releases soon a hotfix to solve this issue