"502 Bad Gateway" when visiting certain URLs

edit

Not sure how to get to this URL, but somehow Googlebot found a way (:

• http://expats.askbot.com/get-tags-by-wildcard/

These seem like they are expecting post data and are erroring when I send a get request:

• http://expats.askbot.com/mark-tag/ignored/
• http://expats.askbot.com/mark-tag/interesting/
• http://expats.askbot.com/set-tag-filter-strategy/
• http://expats.askbot.com/unmark-tag/

When I access any of these URLs on my hosted Askbot site, I get a "502 Bad Gateway" error.