Ok, let's do a couple of things to nail this issue as best we can. Do the following:

1) Run the Repair Filesystem tool from the Extended tools (CTRL + ALT + X) menu from the console. They system will reboot.

2) Then test again to see if it crashes again.

3) If it Crashes again - run the memtest - After system is booting from POST, hit the escape key or tab key. You will get a basic menu to run the memtest - let that run for 1-2 hrs.

4) Run the Demo-CD version of DSS from the website link below. Then test, I want to verify if it is the USB module.

http://www.open-e.com/account/demo/