I am experiencing this exact same problem.  My computer settings have both the computer and monitor power settings set to off (never go to sleep), yet after a period of inactivity, the monitor will go into power save mode. Moving the mouse or pressing a button on the keyboard does not wake it up.  Turning the monitor off and back on gives me the message that there is no signal coming from your computer.  It is not the computer or the graphics cards. Swapping my Dell U3011 monitor out for my Samsung monitor alieviates this issue. Pressing the power button on the computer also does not wake it up.  I have to do a hard reboot to fix it.  My computer uses Windows 7, i7 core 965 with 2 Nvidia GTX570 cards in SLI. I am using the DVI port.

Does the monitor have an independent sleep setting that can be shut off?  Anyone have any suggestions on how to fix this issue I am experiencing?

I’m not sure that we’ve experienced exactly the same problem. My monitor went into sleep mode when I was browsing. It turned out to be the Adobe Flash Player that was the problem. As soon as it had been uninstalled my computer worked fine.

All,

For my notes, you do have the keyboard and mouse plugged in the PC USB ports and NOT the monitor USB ports?

 Chris on my systems the keyboard and mouse are plugged directly into the PC.  

I'm experiencing the same issue as Hopelina posted.  But I'm seeing it on multiple platforms and multiple U3011 monitors.  From my perspective it appears the monitor is going to sleep but the system is not (power management set to not sleep).

My solutions to get it back have been:

1. reboot

2. cycle to another video resolution then back, on my second display that still has video

3. put the system to sleep by pressing the power button then waking it up and the display comes back.

Obvious these are not long term solutions but they have been getting us by.  Suggestions?