When accessing any topics I get the following. I also get a similar error in Control Panel.

*******
Script: /usr/local/apache/htdocs/fmbwww/forums/scripts/showflat.inc.php
Line#: 231
SQL Error: Can't open file: 'ubbt_POSTS.MYI' (errno: 145)
SQL Error #: 1016
Query: SELECT t1.TOPIC_ID,t1.FORUM_ID,t1.TOPIC_LAST_REPLY_TIME,t1.TOPIC_IS_STICKY,t1.POST_ID FROM ubbt_TOPICS as t1, ubbt_POSTS as t2 WHERE t2.POST_ID = 44604 AND t1.TOPIC_ID = t2.TOPIC_ID
*******

I run repair table ubbt_POSTS and I get this:

+---------------------+--------+----------+----------------------
| Table | Op | Msg_type | MsgTxt |
+---------------------+--------+----------+
| fmforums.ubbt_POSTS | repair | error | 28 when writing to datafile |
| fmforums.ubbt_POSTS | repair | error | 28 when writing to datafile |
| fmforums.ubbt_POSTS | repair | status | Operation failed |
+---------------------+--------+----------+

Any help would be a godsend at 5:00 AM EST! *lol*

Error 28 generally means you're out of diskspace (either you're at your MySQL space limit or the disk itself). I suggest you close down your forums and check your diskspace usage and if you're not at your quota, ask your webhost if there is a mysql space limit.