Dock icons vanishing or distorting on rollover

[Bolteh]

I'm having an issue with the dock icons disappearing when I roll over them. It doesn't do that for all apps, but some.

Icons that completely disappear:
- LimeWire
- Contacts
- Quicktime Player
- iTunes
- Spaces
- GearBox (Line6 Amp-sim)
- Amplitube (Standalone Amp-sim)
- Guitar Pro 5
- Garageband
- Texteditor
- Pages
- Acrobat
- After Effects
- Warcraft 3 RoC & TFT

Icons that distort:
- iDVD
- Word
- Preview
- Flash
- Dreamweaver

Screenshot:

Rebooting seems to help, but it comes back after a while. One would think it's the videocard messing up, but I can play games or videos or anything related to video-performance and all is fine. It's just the dock.

Anyone got the same problem and/or solution?