The fonts you set in your documents have no impact on the output produced on the Kindle, so that explains some of that. I guess there's a clash in character sets encoding somewhere in the conversion, I'll experiment a bit with this and get back to you
EDIT: @Alex73: Yeah, I can't get it to convert properly directly through calibre either, even after trying most of the usual romanian character encodings as the input charset... Might be just because I'm missing something stupid in calibre to handle these files ^^ One way to do it, when converting from non-HTML based formats like these, is to export them to HTML/XHTML (Or even PDF... -_-") first, and then use that HTML/PDF file in Calibre. That should work way better. (I tried with the XHTML export from OpenOffice, and that seemed to work fine when converted through Calibre!)
Also, @DX Graphite owners: Is it still a B05 serial? What exact version of the firmware is installed? Any brave souls here wanting to help see if that thing's hackable? ^^