uncalled for reboot

[Z. Wade Hampton]

Greetings to all,
I am attempting to run cvsup-without-gui on a Dell Inspiron 1501, with amd64x2 
processor and 2GbRAM.
I am using the "ports-supfile" modified to suit location and RELENG_6_1.

The process begins, and starts deleting the old stuff...no problem.
Then, about 10 minutes into it, the system reboots all by itself - no apparent 
reason.

Any ideas? 

Season's Greetings,
Z. Wade Hampton
Twin Bridges, Montana