This is due to the changes of the new CUPS 1.4.0 in Karmic. The problem is caused by a new USB CUPS backend. For this backend the "usblp" kernel module must be unloaded.
Edit /etc//etc/modprobe.d/blacklist.conf adding a line
blacklist usblp
and then run the command
sudo rmmod usblp
Now CUPS should see your USB printers again.
This is due to the changes of the new CUPS 1.4.0 in Karmic. The problem is caused by a new USB CUPS backend. For this backend the "usblp" kernel module must be unloaded.
Edit /etc//etc/ modprobe. d/blacklist. conf adding a line
blacklist usblp
and then run the command
sudo rmmod usblp
Now CUPS should see your USB printers again.