XPS 630 Issue - Wacky Shutdown, Sleep, Logoff, Switch User

Ok so this is one I haven't heard about.  From day 1, I haven't been able to use Sleep, Logoff, or Switch User.  All 3 actions do exactly the same - screen goes blank and stays blank. However, the power light stays on as normal! (white as normal)  Moving the mouse or hitting keyboard does nothing.  Only way to get the PC to work again is to hold down the power button until reset.

Recently, a similar thing has been happening when I shut down.  The PC appears to be shut down - but the power light is still on.  It boots up upon hitting the power button but says "Cant POST" and I have to hit F1 to proceed or F2 to enter setup.

Any ideas?  Comp works fine but this is obviously a pain, as is the inability to switch between mine and my wife's accounts.