Seems there was a problem with the ShareThis button code we (and many other sites) use, there were a lot of reports from other sites with similar problems. It was fixed late last week.
As for the site slow down - sorry about that, I wasn't paying attention and it seems that the database server got a bit stuck on something. A restart seemed to fix that.
I'm hoping the upcoming rebuild of ZooChat finally solves the performance problems once and for all - but I won't know for sure until it's finished!