two forums problems

All you have to do is, if you're using Windows 2003 set them on seperate application pools.

Or, if you can't access that simply edit the prefix to be something else. That way they cannot interfere. They don't have to be in a seperate subdomain.

Turning off Application Variables might make it slow. Not exactly sure how WebWiz works with that, as I haven't looked at the code.

Try resetting your database permissions on the mdb file to be read+write. I would recommend putting it outside of the directory or else someone can download your database and ruin forum.