Category URL Problem

I have a problem with the following:

– If I attempt to load a Category page, like so:
https://tpachanoi.org/category/site/

I get a 404 from WP.

This started to occur immediately after I upgraded to WP2.0 (I followed the upgrade steps at https://www.tamba2.org.uk/wordpress/upgrade2two/).

I tried using the rewrite.php plugin from ryan, but when I activated it, it seemed to screw up quite a lot (the admin screens looked like they were from WP1.5, and at the top of each of those screens, there was odd error like text, which I didn’t record…) so I deactivated that plugin.

I do have some output from the dump_env plugin if anyone cares to take a look.

I’m not sure if my problem is similar to some of the issues involving .htaccess; it seems a little different than most of the other posts I’ve seen so far.

Thanks!