Sorry to dredge up a dead thread, but I just spent 5 hours today trying to sort out why Hulu was suddenly skipping/lagging in the audio/video after my Windows 7 install. I have the new Windows 7 Sound Blaster drivers, and this happened anyways. I did what the above post says (put the sample rate up to the highest studio quality) and now there is no lagging.Finally, I tried the absolute highest sample rate (one of the Studio quality rates) and the crackling went away.
So for me, it was a matter of getting the Vista Audigy drivers, possibly disabling audio enhancements, and setting the max sample rate for the audio.
I hope this helps at least one other person out there.
I have no idea why this is the case (I only got serious lag in live-stream sites like Hulu, and minor lag in iTunes) or how this works, but the problem is fixed now. I can still hear tiny skipping every so often, but it's tolerable.
I have not seen this solution anywhere else, so I want to make sure people try this as well. Most people had issues with Audiodg.exe, or with driver compatibility, and this seems to be something else.