MySQL Watchdog warnings that disappear on flushing the cache

I get following type of warnings on my Drupa开发者_开发百科l Site which usually disappear when I flush the cache

"Warning: MySQL server has gone away query: INSERT INTO watchdog (uid, type, message, variables, severity, link, location, referer, hostname, timestamp) VALUES (1, 'php', '%message in %file on line %line.', 

Any idea why it happens and how flushing the cache clears it all?

Thanks in advance!

This issue has been posted multiple times to drupal.org. Best of luck fixing the issue.

Try setting max_allowed_packed = 64M ..... it worked for me.