Error creating ticket: DBD::mysql::st execute failed

I’m getting this error while creating tickets: DBD::mysql::st execute
failed: MySQL server has gone away at
/usr/lib/perl5/site_perl/5.8.8/Apache/Session/Lock/ line 71.

I have removed rt-3.6.6 & dropped the mysql database and installed
rt-3.8.2 (compiled from source). I can log on to rt web interface,
create unew users etc. but as soon as I want to create a ticket I get
this error. mysql 5.0 is running. There is nothing in my
/var/log/mysqld.log log.

Thanks for any suggestions.