Running programs made in C# 4 on a computer that __just__ had .NET framework 4 installed

Is there a wait time between when you can run/install programs made in Microsoft's VISUAL C# 2010 EXPRESS and when they would work without errors?

I just installed it on a m开发者_如何转开发achine running Microsoft XP and when I installed my program, it didn't run correctly. I checked back on my computer, and it ran fine. Someone mentioned something to me once about needing to wait.??? Is this true? If so, why?

I think a new install of the Fx requires a restart.