I hate to tell you this, but the diamond monster mx300 isn't supported.
reference: http://www.linuxdoc.org/HOWTO/Hardware-HOWTO-13.html
However, I will look around for something for you. You never know.
As far as modems, the "big" problem that I had for the longest time was
that the default software IRQ was not my board's IRQ. It took me a long
time to find setserial and /etc/rc.d/serial.
The symptoms are that it takes about ten times as long to get back
status codes from the modem, so everything seems really slow.
I think linuxconf automatically sets that up, though.
--Mike
Michael J. Smith
Flyfisher, Russian Translator, and Linux-Geek-At-Large