Piwik stopped after updating php to 5.3

After my hoster updated php to 5.3 two days ago, piwik does not track anything on my websites. There are no error-messages or something else - just no users.

Any ideas what I can try to fix this?


can you check in you webserver error logs ?
is there anything there?

Also, disable GeoIP plugin if you used it, it might help.