Character corruption in comment submission only

I have a multi-lingual blog that generally works fine (www.realclimate.org). However, if accented characters are entered as comments, they show up fine in preview, but get corrupted when they get entered into the database (lots of A?? and the like), and show up as corrupted on the blog.

In the comment edit area, I can manually correct the problems and have them stick. But recently, people have started posting in Turkish, and that is beyond my linguist skills to deal with. i.e.
http://www.realclimate.org/index.php/archives/2007/02/save-the-world-earn-25-million/tk/

The actual db is saving things in latin-1-swedish which appears to be standard (from looking at other posts here). The blog output is in utf-8 which seems fine (it copes with French, Spanish, Slovak and Turkish).

I don’t have a problem writing posts in other scripts, nor editing comments. It is only in the comment submission step where something goes wrong.

Any thoughts? (and please don’t just say upgrade to WordPress 2.0 or something – I don’t have the time to do that right now).