[syslog-ng]syslog-ng to mysql

Hey, I'am running syslog-ng Version: 1.5.15-1. I pipe all the syslog messages to a mysql database. Every thing works fine, but some times it stop logging to the database. I run mysql Version: 3.23.49-8. When i restart syslog-ng it work fine again. It can work fine for weeks. Have any else experience the same problem ? Regards Tahir