I tried to connect my new Ubuntu 12.10 to my Makerbot 3D printer (using
ReplicatorG version 25) and it couldn't find the printer which was
connected to /dev/ttyUSB0. Running it as sudo worked so I thought it was
a security issue.
ls -l /dev/ttyUSB0 gave the following:
crw-rw---- 1 root dialout 188, 0 Nov 9 19:05 /dev/ttyUSB0
So, in the end all it took was adding my user to the dialout group:
"sudo adduser reece dialout" but the catch was that it didn't appear to
work initially, only *after* a reboot.
I don't recall that I had to do this when my laptop was Ubuntu 12.04 so
be aware that there may be subtle differences in default settings.