Die Ausgaben sind bei mir ähnlich - funktioniert aber trotz "unable to open" ganz normal mit dem RP6Loader und der Port wird angezeigt und kann verwendet werden.
(ohne sudo! Bei udevtest ändert sudo nix wie man unten sieht)
Ubuntu 7.10 in VMware und auch normal installiert ohne VMware.

Code:
user@ubuntu710desktop:~$ udevtest /dev/ttyUSB0
This program is for debugging only, it does not run any program,
specified by a RUN key. It may show incorrect results, because
some values may be different, or not available at a simulation run.

parse_file: reading '/etc/udev/rules.d/00-init.rules' as rules file
parse_file: reading '/etc/udev/rules.d/05-options.rules' as rules file
... bla bla 
parse_file: reading '/etc/udev/rules.d/90-modprobe.rules' as rules file
parse_file: reading '/etc/udev/rules.d/95-hal.rules' as rules file
parse_file: reading '/etc/udev/rules.d/99-udevmonitor.rules' as rules file
parse_file: reading '/etc/udev/rules.d/libmtp.rules' as rules file
unable to open device '/dev/ttyUSB0'


user@ubuntu710desktop:~$ sudo udevtest /dev/ttyUSB0
[sudo] password for user:
This program is for debugging only, it does not run any program,
specified by a RUN key. It may show incorrect results, because
some values may be different, or not available at a simulation run.

parse_file: reading '/etc/udev/rules.d/00-init.rules' as rules file
parse_file: reading '/etc/udev/rules.d/05-options.rules' as rules file
... bla bla
parse_file: reading '/etc/udev/rules.d/90-modprobe.rules' as rules file
parse_file: reading '/etc/udev/rules.d/95-hal.rules' as rules file
parse_file: reading '/etc/udev/rules.d/99-udevmonitor.rules' as rules file
parse_file: reading '/etc/udev/rules.d/libmtp.rules' as rules file
unable to open device '/dev/ttyUSB0'


user@ubuntu710desktop:~$ ls -l /dev/ttyUSB0
crw-rw---- 1 root dialout 188, 0 2007-12-18 18:45 /dev/ttyUSB0
Ich teste das gleich mal noch unter Debian, OpenSuSE und Fedora.

MfG,
SlyD