One time RDR's database got bloated by a plugin that didn't work right. Bloated to the point that it exceeded the memory allowed for mySQL

I hope that isn't what's happening with you.

All better wp-super-cache saved the day. Strongly recommending it to wp bloggers now.

Yes, be careful what plugins you use and don't use what you don't have to. WP is already bloated

I think it's all the photo album stuff, only the sites heavy in photos have been having problems.