Hi!
Reinstalling UWS was not necessary - you could just run
UWS.RegRepair.exe ("Repair Server Configuration" from UWS Programs menu folder): it re-ACLs temporary folders and does a few other things that sometimes need to be done out of band.
Since your application is .NET 4 specific, you could work around the issue by modifying UWS VS Setup Project prerequisite and make UWS prereq
depend on .NET Framework 4. The downside is that you would need to modify UWS VS prereq file after every installation of UWS on a development box.
Best regards,
UltiDev Team.