Short update:
Site is under ddos, traffic was around 40Mbit/s, so mysql crashed -> getwork server crashed too. I solved it by shutting down the site, so mining is working again. I'm a bit hurry right now, so this solution must be enough for this day, I'm very sorry for troubles. I'll try to fix site (maybe some requests/s limiter per IP?) afternoon UTC...
People are idiots...
Thanks for the update slush. I for one appreciate the work you do, and I think it is sad that some lowlifes have nothing better to do than to DDoS your site

The request limiter idea sounds like a good one to me. Maybe even have some method of banning abusive IPs?