Hi Adam,
Yep, I've seen this one myself.. I also believe a similar error was reported
here about a month ago. Obviously one more item on an ever-growing "to-do" list! :o)
Looks like a bug in the error handling routine. The same funky appearance (extra sidebar) was happening if you made a mistake in constructing a poll.
I'm reliably informed there will be an overhaul and upgrade on the site's templates in the near future. So hang tight! :o)