Urgently: MySQL server has gone away

Hi.

I updated just now from plesk 12.0.18 #74 to #80 and now I get all minutes error mails with
"mysqli::query(): MySQL server has gone away" and database is corrupted... not so funny.

Is here a bug in the update software for mysql?

I restart the server but still a CHECK TABLE is not possible, I get always "server has gone away".

autorepair not work. result after few tables:

mysqlcheck: Got error: 2013: Lost connection to MySQL server during query when executing 'CHECK TABLE ...


EDIT:...

Urgently: MySQL server has gone away