What browser are you using? We actually just noticed this with the Like button using Safari on one of our sites. This didn't occur before, which means that it could be a change that Facebook's implemented, and/or something that we need to catch up on.
We're investigating, but we're not seeing it on the same site in Chrome or Firefox. Let us know, and (like a few of the other posts you've made), we'll be investigating. Sorry for the troubles!