Hello- I have the newer atahualpa, and my plugins are... akismet,bastsats,customizable permalinks,sociable,wpdatabase backup,wp-cache and generic footer- all the latest versions.
first- the page redirects, then it tried to reload every 3 seconds. a user caught it with her security feature and when I raised my security levels, I found it, too.
I thought it was the header rotation,trying to rotate while people were watching- but I removed all but one header image and that didn't help.
I also thought it might have been a random quote rotator, but deactivating that didn't help either.