I received a comment recently tipping me off to a bug in my Virtual Multiblog system for WordPress. In certain cases, the system will show one particular blog no matter which address you go to.
If you’re having this problem and you’re using the $vusers list, try changing the order of the $vusers list. This alone may fix things.
I’ll try to get a “real” fix out soon (probably this weekend). A new version should be coming out anyway within days. 🙂