Log into your phpAdmin and enter the following...
REPAIR TABLE `YOUR_TABLE_NAME` That should repair your damaged table and allow you to get back into it - I'm guessing that you are running an older version of phpAdmin such as 2.2.x (or anything PRIOR to 2.5.x)
I hope this helps
...notes, if your DB is HUGE and the server is SLOW, you may have to run that command a few times to get it back on track