Hi,
Just an update. I didn't get any answer from Jens yet, so I assume he's busy. I've had some time tonight to see if it's just AmiPPP that's having problems with silversurfer.device, so I wrote a short program in Blitz Basic that opens the serial.device and then the silversurfer.device. Serial.device returns a non-zero value (which is good), but the silversurfer.device doesn't, so obviously it's almost certainly a HW problem.
I also tried an older version of silversurfer.device from the included driver disk and the latest version from Jens' site, but all gave the same results. I'm guessing that the clockport adapter is busted. Unfortunately I haven't found a way to test for the presence of a clock port, but I've just ordered a new one from Vesalia and will know soon enough.. I'd really like that hardware accelerated, faster serial port on my A500!!