$bbuserinfo['usergroupid'] (USE THE QUOTES!).
Code:
mysql> select usergroupid,title from usergroup;
+-------------+-----------------------------------+
| usergroupid | title |
+-------------+-----------------------------------+
| 1 | Unregistered / Not Logged In |
| 2 | Registered |
| 3 | Users Awaiting Email Confirmation |
| 4 | (COPPA) Users Awaiting Moderation |
| 5 | Super Moderators |
| 6 | Administrators |
| 7 | Moderators |
| 8 | Banned by Moderators |
| 9 | newforum Developers |
| 10 | WDF Project Designers |
+-------------+-----------------------------------+
10 rows in set (0.19 sec)