After upgrading NSIS installer software from version 2.46 to 3.09 and usage of the same scripts on same computer we get different UAC_GetIntegrityLevel value:
NSIS 2.46: UAC_GetIntegrityLevel=0x3000
NSIS 3.09: UAC_GetIntegrityLevel=0x0
What has changed?
We upgrade NSIS installer software and UAC plugin
NSIS v3.09 is Unicode by default.
If the problem is fixed by adding Unicode False to the top of your .nsi then you put the wrong UAC.dll in NSIS\Plugins\x86-unicode or your .nsi has !addplugindir ".\plugins\x86-ansi" somewhere in it.