Cannot Dump / Backup Attachments Table

Hi, maybe this is more MySQL than RT…
I have some sort of corruption in my attachments table. I cannot backup,
dump or query above row 788 in that table.
Backups or mysqldump result in the same thing:
Error 2013: Lost connection to MySQL server during query when dumping table
Attachments at row: 788

Rt still runs fine, well except I cant backup the db.
Anybody seen this before, have a way of getting the table malleable again?