Windows 7 won't wake up after sleep

I'm got a new Dell XPS 9000 desktop running Windows 7.   The system is set up to automatically shut down the display after 30 minutes and then put the computer is sleep after 2 hours.  That works fine, however, when trying to wake up the computer after sleep, I heard the fan starting up, but nothing else happens.  No display ever comes up.  I am forced to shut the computer off (using the power button) and then restart it.  When it does start up, it's resuming from sleep mode.

There have been a number of postings about Windows 7/sleep problems, but they are all a little different.

Anyone have any thoughts?

Thanks.