exim4 MTA mailq stuck..

HI,
I've got the following problem with my HD-installed
Knoppix 3.2:
I exchanged the MTA sendmail with exim4 which more
fits my needs. I just got one error in my configuration
and I don't know why. My eMail gets properly fetched
by fetchmail and sending is no problem too, besides
that all of these messages are hanging around the mailq and don't
get delivered. So sending doesn't work and receiving depends on the Queue too, which is stuck. Anybody knows a solution to this problem?