Blender 2.5 temporarily freezes after render

I’ve been having this annoying problem ever since the alpha, and I have no idea how to fix it.

Whenever I render something blender will “freeze” in a sense. I can’t do anything in it until I shift focus away from blender, and then back. The odd thing is that is seems like the program is still running fine, cause if I scroll, or move around, it updates to that once I shift focus back to blender.

I’ve had this problem on 2 PC’s now, one with XP, and the other with 7.