Hi Rick
The common thing in the boot process is,when the "OS/2 Square" shows up, use "Alt+F1" for the menu, or "Alt+F4" to go selecting one by one which things run from the config.sys.
If "Alt+F1" is working, go to the command line, and "tedit config.sys" and remove the driver that is producing the trap. I haven't use SIO in a long time, maybe there is some VSIO driver you need to REM out.
Or is it that you can not even get to the "Alt+F1" menu?
Regards