I'd start with the Apache mailing lists. Anytime I am troubleshooting a specific system I go to the source. I suspect you're going to be looking at the # of child processes being spawned and how many requests they're allowed to handle. You might also look to see if you're doing any url rewrites as they can soak up CPU pretty quickly. Frankly I think 1.1 GB in Ram is a little thin for what you're describing but then I tend to overbuild...so what do I know?