Ah! I've also seen something like that - the debugger is itself a form, with its own Activate event which is fired somewhere in the mix, breaking the spell. What's in your Form1 Deactivate and Form2 Activate, or any LostFocus / GotFocus, Show, etc. The coverage profiler will tell you what code is firing. I submitted a bug like this which was not fixed in 8 - if you call a SetFocus somewhere, try commenting it out for the moment to see if the problem goes away.