if your MySQL process is running, stop it. On Debian:
sudo service mysql stop
Go to your data folder. On Debian:
cd /var/lib/mysql/$DATABASE_NAME
Try running:
myisamchk -r $TABLE_NAME
If that doesn't work, you can try:
myisamchk -r -v -f $TABLE_NAME
You can start your MySQL server again. On Debian:
sudo service mysql start