When I try to "become" a user, I simply get sent to the Main Page, the "Extra Information" portion of which indicates that I'm still me.

Furthermore, the fix Rick posted on 18Jul02 here doesn't appear to cause any change in behaviour.

The thread you referenced has been changed. The safest thing to do is always make sure your cookiepath is set to "/". When I made the cookiepath adjustable it ended up causing alot of problems

Yep, the latest posted fix does the trick!

Thanks.