Hey there lady...
Have to admit to never using qtt taskbar but these two freeware programs might be able to help you out. I've been having issues with my png files not displaying as thumbnails so I've gotten myself into searching for the same type of problem. Mystic Cooler
- Generates thumbnails in explorer as well as your right-click menu
It's available in both 32 and 64 bit and I've been running it on my copy of Win 7 with no problems. And you might want to also check out - SageThumbs
- Same solution basically as the other one but it's from the people
that are responsible for the xnview project. So I hope they help you - and if I can think of anything else I'll let you know. I know what a pain in the ass graphics and Windows 7 have become - Good Luck!