[Tigga]

Littlebit - Did you upgrade from v3.0 or 2.0? If I remember correctly, the $username variable was used in versions 2.0 and earlier, but should have been $bbuserinfo[username] in v3.0 and 3.1. It was changed just to remove a small bit of code that wasn't really necessary.
For the logged in users, it sounds like you may have missed a step in the install file, or perhaps the template could have been reverted to it's original. If you'll edit your forumhome_loggedinuser template and add $bburl at the beginning of the code for the link it should fix that right up.