an unknown error occurred (-4)

I'm getting this same error while trying to download a movie rental and access my iTunes account. Anyone got any ideas?

I'm having the same error while trying to get my Digital Copy from the "Family Guy presents Blue Harvest" DVD. I have iTunes 7.6 and Quicktime 7.4 installed. I also got the same error message while trying to download the "Single of the Week". I could access the store to browse and I was able to download Podcasts.

I'm getting the same error when trying to sign in to iTunes. It keeps toggling between unknown error -2 and unknown error -4. Very frustrating. I've been having this issue since Tuesday (1/15) evening after upgrading to iTunes 7.6.

Some folks say that iTMS is being overwhelmed by the large number of users and they were finally able to get through by retrying -- though if that's the case, it's just going to make the problem worse. As far as I know Apple hasn't admitted to any issues yet, but there is definitely something going on based on all of the reports in these forums.

I don't know if it has something to do with it, but I was finally able to redeem my Digital Copy of "Family Guy Blue Harvest" after reverting to Quicktime 7.3.1 using "Pacifist". I just get a warning from iTunes saying that I need QT 7.4 to rent movies, which I don't plan to do soon anyway.

Josh,

I'm glad you were able to get back in. Unfortunately there are still a large number of folks affected. See this thread for more info:

http://discussions.apple.com/thread.jspa?threadID=1338204&tstart=30

From what I've gathered there was a server migration last weekend (1/12-13) and the accounts which were migrated to the new server were either corrupted or the new server has not been properly integrated into the iTMS system.

Note "solved" answer.
The problem has been occurring for the last three days on my new iMac.
Solved?