The monitor is a Dell 1908 Ultrasharp WFP operating digitally, the computer is a HP Pavilion a6220n, and the operating system is Vista Home Premium.  When I first start the system and very quickly turn on the monitor and computer boots normally.  If I am a bit slow to turn on the computer the monitor displays a message that the monitor is entering power save, the power light changes to yellow and the computer then enters sleep mode.  Once I get the computer out of sleep mode the monitor light turns green and the computer and monitor boot normally.  Once the computer and monitor are on and working both work fine. 

I have already up updated the bios, Disconnected then reconnected the monitor from the computer, checked connections for damage, reset the monitor to factory settings, and changed the resolution.  Any ideas?