Studio 540, working but no display

My Studio 540 boots up fine and is on my network. The screen goes black after showing the logo. Turning the monitor off/on get a 1 second display then black again, same on another monitor. I can click on programs and the open up and star/power/restart/shut down functions work also. Cleared cmos and reset bios without results. Also, BIOS and Startup Options screens display fine and function.