Hmm... 2 questions for you then, if you don't mind.
1) Do you have any GSDs actually working in 10.04?
If yes, then 2) In webadmin -> wizard -> devices -> Generic Serial Control Devices..
under Device Data, in the COM port dropdown, what options is it giving you? Mine is showing the correct PCI address, but not the right /dev/ttyUSBx address.
I'm not sure this is actually the cause of my problem, but I'm running out of ideas.