Site Showing Errors.. Aparently

Hi all,

My website is currently showing JS errors.. apparently. I can't see them, admin can't see them, but half our users can.

I was just wondering if someone could take a look:
http://www.birdforum.net
and see if you can see the errors, and what may be causing them.

People started complaining after we installed Bira's away hack, but to be frank our board is so 'over-hacked' that that's probably a coincidence.

Many Many Thanks,
Oliver