IDirect3DDevice9 Release deadlock

Question

What could cause this? I use direct3d9 from a dll on windows 8. No calls originate from DllMain.

All calls to the api and winapi for my window are done from the same thread. All ressources associated with the device were freed.

Answer 1

In case anyone else gets this not really helpful behaviour out of his program:

This issue was caused by the window of the device being not properly destroyed.