Yeah, in a nutshell your Posts table is corrupt but the repair table didn't work for you.
Error Number 28 = No space left on device
Is the drive that MySQL runs on full? Or are you close to your quota with your webhost. - that's why it might not allow you to reapir the table.
The commands astaran posted would be done at the server level, not any SQL interface. If it's not your own server, ask your host for this.