Module julian: error

Trying to show event with id 1:

http://www.gruenemuenster.de/index.php?module=julian&func=viewevent&cal_date
=20081127&event_id=1

I get this message

http://www.gruenemuenster.de/index.php/base?code=8&exception=At:%20/homepage
s/42/d23929904/htdocs/gruenemuenster/modules/julian/xaruser/viewevent.php%20
(Line:%20178)%0AUndefined%20index:%20%20eCalendarID&product=&component=&func
=systemexit

what can be the reason?

I removed the Julian module, installed again with new files on the server,
but the error is the same.

On other sites there is no problem using Julian.