When I have my pl2303 adapter connected to the USB on my OS X 10.4.11 PowerMac G4, if I leave my Mac alone until it goes to sleep, it will lock up if I try to wake it up.
I am using V1.2.1 of the pl2303 driver.
Forgot to mention:
System Profiler shows this for the USB-serial device:
Bus Power (mA): 500
Speed: Up to 12 Mb/sec
Manufacturer: Prolific Technology Inc.
Product ID: 0x2303
Vendor ID: 0x067b
Have you already tried a newer version of the driver?
I am unaware of a newer version than the one I mentioned in my original message. Do you know of one?