I had an interesting error message today!

mysql Table ” is marked as crashed and should be repaired

The solution was easy enough. Go to the directory of the database, type:
myisamchk *.MYI -s
This will check all tables. For those that need to be fixed:
myisamchk -r tbl_name

Source: http://dev.mysql.com/doc/refman/5.0/en/myisam-repair.html

Also this link went into a little more detail on why it happened and what you can do to minimse it happening again:
http://www.softwareprojects.com/resources/programming/t-how-to-fix-mysql-database-myisam-innodb-1634.html

Rock on!