I've found a workaround for myself for this one but just wanted to put it out there. When a query fails watchdog is used to insert it into the DB, which is fine 99.9% of the time, until that .1% bites you. The problem is that if the query (say inserting a new record into the "cache") causes a query that is larger than the MySQL query buffer limit. This results in a MySQL error that the query is too large to insert, which watchdog then picks up and tries to insert, which fails, which watchdog picks up ... and you get the point. Result? Infinite loop and then either a timeout or PHP runs out of memory and dies. I'd think the proper way to handle this would be to have a check that the specific error code for a MySQL error resulting from a query buffer violation doesn't try to insert the query, again just putting this out there.