Windows don't draw, they are just white

I got a bug report from a user, but I can’t reproduce it. Hopefully someone else has seen it and might know what causes it.

On an intel mac running 10.5.6 the user says nothing draws, each window just stays white. The app is responsive, but nothing draws.

Any ideas how to debug this? I can’t reproduce it.

Here is a jumbo screenshot I was sent:

Sounds like our old friend: