>Can anyone tell me if there they've run into any trouble running code that was compiled under VFP 5 with the VFP 6 SP3 runtimes?

Ahh, I've never tried it, but I wouldn't suggest it to my enemies. All you can do is test it though.

>I have an application that's 2 years old, that was built using an application framework that didn't supply full source code. So I'm kind of stuck in that I can't recompile the app in VFP 6.

Maybe something like ReFox to decomile it?