On occasion I experience a freeze up with my CompuTrainer.
You serial port(s) may be going into power save mode and/or need to be optimized.
Please read the following doc on USB Ports Locking up:
Read the following for optimizing your serial port:
With both docs, each serial port needs to go through those steps so it can be a little time consuming if you have a bunch. You will likely have a better experience making these changes.