Error 500 on using tracking for domain with piwik in subdomain

Hi,
I am using Piwik in a subdomain analytics.my-domain.com for several website I have. No I use this analytics for the same my-domain.com. When accessing I get error 500 from the script. Themes like an DNS resolution problem. Can somebody give advice?

Olaf

any idea?

error 500 -> to get more info check your web server error log ?

sorry, my fault, the script returns error 500 if site ID is wrong, i fixed it.
I joint 2 Piwik installations - this caused the problem