If the PC thinks the USB/serial adapter is a mouse, there is a fix for that. I had the same problem. Open the device manager and look for a strange device (I think it's a Microsoft pointing device of some kind) under Mice and Pointing Devices. You may have to turn on Show Hidden Devices on the View menu. Disable, not uninstall, it.
I'm using two USB/serial adapters, one from Bafo and one Radio Shack, and the only problem I have is I have to unplug and replug one of them occasionally if it isn't recognized by the program.