well what i use them for is my pool tables. I run them to turn on the table lights from a program...
It sounds like you are using the interface to manually turn the lights on and off from the PC (as opposed to using timers or macros).
There is an even easier solution, I think.
Rather than get a second CM15A, you can probably get away with just a CM19A, put it on the second PC, and leave it connected.
you should be able to open up AHP on the second computer, and control the lights with that.
If, however, you are just using it for timers, and/or macros that are stored in the interface, then the timers should continue to run, even if the Pc crashes.