[chrishajer]

I wonder if the forums/forum/ is messing things up? Slug based permalinks seem to be working fine.

You can add a line to your config.php to enable debugging and see some additional info which might help. This will be displayed at the top of your forum page:

REQUEST_URI:

should be:

full permalink:

PATH_INFO:

 

Set this in config.php, after the database connection details.

$bb->debug = 1;