Every time I start a game or application that uses DirectX (specifically Direct3D) in any way shape or form, the screen freezes for about 30-40 seconds. Everything then seems to work normally. The same thing will happen again when I quit the game.
This does not happen for OpenGL-based applications - only DirectX ones.
I am using Windows Vista Home Premium 32-bit SP2 and my video card is an NVIDIA GeForce 8400M GS. I have the latest driver from NVIDIA (184.108.40.20632 A).
The PC itself is an HP Pavillion dv6757ca.
What could be causing this?
Update: I tried running Windows 8 (the developer preview) on the very same machine and... it works! The issue completely disappears. So I can only conclude that the problem was with Vista or the drivers since everything works fine now.