Howdy - when I go to submit a comment on my site, and press submit, I simply get a page saying

Not Found

Sorry, but you are looking for something that isn't here.

What seems to be the problem, do you think?

what are your permalinks set to?

they are set to /%category%/%postname%

Did this just happening?
What version of atahualpa and wp?
Have you tried deactivating all plugins?
Does it happen with the default theme?

Yes, it must have started happening a while ago. It turns out the same issue is happening with the default theme. I have no idea why, but it's really very annoying...

Ok, turns out the Comments database was corrupted...all fixed now