I never thought it would be possible, but apparently you can run the Visual Sequencer from a Mac!
Thanks for your help. After poking around on the VMWare forums and elsewhere I decided to get a different USB <=> RS-232 adapter instead of my old KeySpan adapter. It would appear that there are many of these, but the key is to get one that has the Prolific IC PL-2303 chip set. I got mine here: http://www.sparkfun.com/commerce/produc ... ts_id=8580
Using this adapter, the Visual Sequencer 1.16 connects just fine with SSC-32 from my MacBook Pro running VMWare 1.1.3 on OS X 10.5.4. My VMWare partition is running Windows XP Pro SP2.
This adapter also has drivers for Windows and Linux.