I had a problem previously with MySQL hanging with CPU usage down to 0. With teh fantastic help on ExpertsExchange of mwvisa1 he managed to identify it as an issue with query cache
set too high - please see http://www.experts-exchange.com/Database/MySQL/Q_27283597.html
Problem seemed to be fully resolved by setting query_cache_size=0
and it's been running fine now for about 6 weeks.
Now suddenly out of the blue, it has started happening again!! Arrrgggh! The setting hasn't changed and noting else of note has changed either.
I'm at a real loss here, I though we'd nailed this problem and now I don't know where to start!
Any help would be very very welcome