TrackingAPI: Error 500 when using GeoIP-Plugin



I have installed GeoIP today in my Piwik 0.9.
The mod_geoip module is not installed, because I have no access to the server.

When the plugin is enabled, the API returns a HTTP-Error 500.
I enabled PIWIK_TRACKER_DEBUG and saw that the script stops after writing out “New Visit.”.
Normally there is more output…

What could be the problem?

Sorry for my bad English…