I have seen the same issue after a power outage, using a known stable O/S (Win 2K3) that does not do this on other machines. I built O/S images sequentially, monitoring for stability in between and am almost certain that this is caused by unstable drivers for either the generic USB mouse/keyboard and/or Intel GigE drivers.
I would suggest using a PS/2 mouse and keyboard and DELL ENET drivers to start. (Intel drivers blue screen the O/S repeatedly). If you still see the issue, then contact DELL to issue an ENET driver update.