There are a few things that are missing here. When you say you've rebuilt the app, am I correct in assuming that you have updated the version of .NET that you are using? Similarly, how are you distributing the application?
Have you checked event viewer to see what's being written out here?
Ultimately, my suspicion is that you are going to find that this is a dependencies issue. To investigate these, I normally use
Dependency Walker (depends.exe)[
^].