I've never seen this sort of problem before. But if your system is sending valid jpg files to Excite for your home page but you can't see them properly than it's a display problem rather than rendering. Also you are getting bad results in IExplorer and whatever software you use to view your dig cam pics -- so it doesn't sound like an image viewing software problem. You tried 3 different vid cards so it is not a bad vid card.
That pretty much leaves a problem with a vid card driver. Follow Smoke2jj's advise. That's my guess. But don't forget to uninstall your old drivers before reinstalling the new.