Why does mobile Safari revert to "Never accept cookies"? Every few days Safari on my iPhone (iOS 5.0.1) reverts to "Never" accept cookies. I put it to "From Visited" but it switches back shortly thereafter.

Discussion elsewhere suggests an Exchange link may be at fault (and I do download email from a work account) but nothing conclusive.

This problem breaks logging in to most web sites.
Possible fixes:

Make sure there are no restrictions on cookie permissions, if you are a part of an Exhange account.
It has been reported that turning off iCloud Bookmarks may fix this issue. To do this; Tap Settings > iCloud and then tap the Bookmarks slider off.