Thanks!
Well, it appears that it's due to a spambot trying to log in under your account. It's probably searching the membership list and then extracting names from it, and then trying to log in with random letter combinations (the so-called "brute force attack").
All I can suggest is make sure that your password is unguessable. If it's a word, consider adding some numbers and punctuation marks to it. It won't prevent the problem described in this thread, but it makes it less likely that the spambot will succeed in logging into your account, and then posting all sorts of junk under your name.
You can read more about it here:
Security Announcement - Login attempts exceeded