SQL table problom
 

OK tonight ar 20:14 PM (israel clock GMT+2)
i got an a my sql problem that said post table had crashed.
the post table was deleted.
no one exept me and my partener can run queries so it's very very strange.
the mysql problem:
Table './kaktos_forum/post2' is marked as crashed and should be repaired
how can i repair it?

for my luck i had a backup from 20 houers before.
i will be glad if some on can explain me why it happend.
and how i prevent it from happening again.