I've been struggling with this problem for two days and I can't figure out what is wrong. The problem seems to be around for 1-2 months but only now have I noticed it.
I am using WordPress 3.1 RC1, the website we are talking about is http://www.notebrother.com.
The issue goes like this:
I am using custom permalinks that have the following structure: /%year%/%monthnum%/%day%/%postname%/
All posts work fine with this permalink structure so I suppose this is not a .htaccess problem.
However if I try to access a category archive, let's say http://www.site.com/category/news/ I get the following error:
Error 404 - Not Found
We're very sorry, but that page doesn't exist or has been moved.
Please make sure you have the right URL.
This problem disappears if I revert to the default permalinks. Using http://www.site.com/?category_name=news works all the time, regardless of what I am doing to the permalinks.
Also if I want to use %category% in the permalink structure, this will make all posts inaccessible, but without an error, the server will simply not be able to process the request and act as if it's down.
I tend to believe this might be due to a bug in version 3.1. Please, any help would be greatly appreciated.