Of course that now means possibly fighting to get a Dell tech out to look at it been there before. I'd be looking for software issues first though.

I doubt it's a network issue. Unplug the cable for a sec and see what happens is an easy test.

I'm a bit lost for ideas really. When it happened to me I was looking for software issues. Our PC supplier was reasonably certain it was the mobo - they replaced it and all was good.