I'm developing a WP-mu based site, and I'm creating my own themes.
Some of my blogs give me a 404 error when I look for single posts. For example: on http://sitios.diinf.usach.cl/tips/ the Pages works like a charm (using only index.php). However, the single posts doesn't work (with the same template).
Thinking it was a problem with my theme, I changed to Kubrick. However, it does still fail, giving a 'nice' 404 error.
By the way, I'm using the directory based approach