Hi alex,
Just to be sure, are you able to insert other USB devices without issues in those computers? If you have issues with other USB devices, then it could be the USB ports that may have something wrong. You tried it on two computers, but if they are the same model, that could still be a possibility.
If other USB devices works fine, and it's only the dongle that makes the computer crash, and you've tried on more than one computer, then it sounds to me like the dongle may be broken, or something in it got corrupted. You might want to contact your PSM sales rep, and ask about dongle replacement, and they can look into giving you a new replacement dongle.
If you'd like to do further troubleshooting before asking for dongle replacement, then feel free to contact our Technical Support department at 1-866-348-5863, or use the web page:
http://printshopmail.objectiflune.com/en/resourcesRegards,
Raphaël Lalonde Lefebvre