Currently Being ModeratedMay 4, 2012 7:17 AM (in response to gestone)
It appears that the Aperture problem was due to a corrupted image stored in MobileMe that was being accessed when Web albums were being synchronized. Deleting the album containing the corrupted images seems to have resolved the problem. I've been running for a few days now without any problems.
The iCloud System Preferences is another, unrelated problem.