Wow. I thought I'd give 2.5 a try. I'm experiencing some really - REALLY - odd issues, and to tell the truth I'm not sure if it's 2.5 or something else that's amiss. But, here's where I'm at.
(Preface: this is not a "fresh" 2.5 install, but rather an upgrade from 2.3.3 using the autotmatic upgrade plugin. So, that has to be taken into consideration. Notable: when using the upgrade plugin everything went smoothly until it got to the database. I got the screen that said my database was not up to snuff (even though my understanding was the database did not change for 2.5??). However, when I clicked on "upgrade database" it went so fast it really didn't look like anything happened.)
So, here are my very VERY strange problems. First, category 404 errors. The categories exist, they have posts in them. but clicking on category results in a 404 - for SOME of the categories. That's what throws me - I would think it should happen for all of the categories, or none of the categories. But *some* of the categories??
Next, the categories that do work - I do not get a category "list", but just the last post in that category.
Before anyone says "theme issue" - I tried different themes (rigt now I'm using WP classic) and the issue is identical in each theme. Some category 404 errors, and only the last post in "good" categories.
I also have all of my plugins disabled (except one necessary one).
I suppose it's possible a plugin I installed did wome kind of internal modification that is causing this. But, I can't really guess what it would be.
So, anyone can tell me where to look? This is really perplexing and irritating.