[Mongrel] Mongrel dying daily with Ruby 1.8.6

[Pete DeLaurentis]

Hi guys,

I've been running mongrel for a while now with Ruby 1.8.4, and last  
week upgraded to 1.8.6.

Since upgrading, each morning when I wake up there's a big problem:

1. Accessing the site returns a "500 Internal Server Error"
2. All the mongrel_rails processes are still running, but none of  
them are active (when I run top)
3. Lighttpd and pound are still running nicely
4. There's plenty of free RAM
5. There's plenty of free HD
6. When I restart mongrel, it all starts working again

I haven't seen anything like this before.  Does this sound familiar  
to anyone?

Thanks for the help,
Pete