Oh, boy. They messed up big time. The good folks at WordPress discovered that some 2.1.1 releases contained a trojan horse added by a cracker. Consequently, they prepared a new release, 2.1.2, which also has some minor updates.
Thankfully, close inspection of my WordPress sites (my church’s and this one) did not show anything beyond the usual, but I upgraded it at once. If you have WordPress 2.1.1 in production somewhere, upgrading is strongly recommended.