I now found out what caused the error in my case. It was the driver for a DVB-C USB-Stick that I installed. After uninstalling it everything works fine again.
Sorry for that. a. -- 84 Things you do NOT want your System Administrator to say: 23. Do you smell something? -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org