Some new info: As I said - changing permission on /dev/ulpt0 from 660 to 666 makes my printer print crap. But in the /var/log/cups/error-log the "permission denied" error is replaced by this one: E [18/May/2008:19:36:08 +0200] [Job 15] Unable to write print data: Input/output error Any ideas, how to solve this?