Hi,
I just installed Ext Designer on my win XP and it crashes too. Here is the error signature:

AppName: ext designer.exe AppVer: 0.0.0.0 ModName: qtcoreext4.dll
ModVer: 4.6.1.0 Offset: 00095227
I don't know if it's happends only for the trial version!
Any Idea for fixing this issue?