Tested@
Model: WL-500W
Firmware: Oleg's Firmware 1.9.2.7-10

Device WORKING with updated pl2303.o
Brandname: Dynex
Brandtype: DX-UBDB9 16" USB PDA/Serial Adapter Cable
USB Interface: USB 1.1 compliant
URL To manufacturer: http://www.dynexproducts.com/
URL To product: http://www.dynexproducts.com/pc-197-...ter-cable.aspx

Old versions of the pl2303 driver don't support the stty onlcr option. As a result, it's impossible to translate end of line to CR, LF and the serial port cannot be used for a terminal. The backported pl2303 driver I linked fixes the problem.