Since the driver is included with Linux, perhaps it changed in 11.04 , although according to the FTDI website it's been the same driver for years. Still, you might want to download from the FTDI site and compare versions:
http://www.ftdichip.com/Drivers/VCP.htm
I'm on Ubuntu 12.04 but I don't have an NG handy. I imagine this would cause trouble on any of the the Arduinos that use the FTDI. I'll see if I can check this out.