Emulator

What steps will reproduce the problem?

1. Start F-Zero GX using the DX9 plugin with VSync enabled.
2. Enter a race, and wait for the hang.

Dolphin version with the problem? Other Dolphin version without the
problem?
r5984, but it has been like this since forever.

32-bit or 64-bit and any other build parameters?
64-bit.

OS version and versions of tools/libraries used?
Vista x64.

Please provide any additional information below.
ATI HD5850, Core i5@4,1GHz, idle skipping, dual core, framelimiting to 60FPS, 4xSSAA.
The game plays constantly at full speed. However, without VSync there's some heavy stuttering here and there, not caused by anything but the frames not being displayed at the correct time. With VSync on everything is butter smooth, and when a game like F-Zero GX runs smooth as silk the game experience is an order of magnitude better.
I though this would be caused by my shitty Windows, but a fresh install of Vista x64 didn't fix it.