It seems US Robotics has fixed the problem in the latest firmwares.
After updating my USR805464 to Firmware Version 4.150.10.15.3 I can print now without problems.
Also, for my USR9108A I found in the release notes for BETA Version 1.8 one point:
Printing issues with operating systems using Cups 1.2.x and 1.3.x
It seems US Robotics has fixed the problem in the latest firmwares.
After updating my USR805464 to Firmware Version 4.150.10.15.3 I can print now without problems.
Also, for my USR9108A I found in the release notes for BETA Version 1.8 one point:
Printing issues with operating systems using Cups 1.2.x and 1.3.x