Remember the ICP can only do 9600 bps or lower, unlike previous models that could do 19.2, 38.4, or higher speeds. I have never seen a maintenance port go bad on the ICP, and I have installed LOTS of them, not to say that it can't go bad but it would very unusual.
I know almost every Dell laptop we had had the serial port go bad though, and had many USB serial interface cables go bad as well, I switched to using nothing but Edgeport serial devices and they have never failed in over 5 years of constant use.