I haven't tested it on other installations yet, but I had this problem that when I tried to edit the newsletter template. It showed the "are you sure you want to do this error", I checked with firebug and the nonce check fails. This happened every time I tried it, I logged out and tried it in different browsers as well but I always got the same error.
If tracked it down to w3c total cache (0.9.2.11 version). Simply disabling object caching fixed it. :slight_smile: Maybe this will help some other people as well when they run in to this problem.