I work at a university as tech support in the simulation center - a lot of A/V work.  I originally started off with a AiO 7450 and two displays (S2740L) - one from DP to DVI and other from HDMI to HDMI.  The issue I have is when the computer wakes up from sleep or computer lock or whatever the screen that is plugged into the HDMI port does not wake up.  It is not giving a "energy saver" message or anything - it is just black (so it is receiving something "outside" it's range).  The only fix I found that works is unplugging from the monitor and/or PC and re-plugin to get a image.  Everything I have tried, gave computer new image twice, swapped monitors, swapped cords, new cords, dell driver/application from support page for monitor.  I then switch to a 7460 for a week; worked through the same motions as before and it still happened everyday.  I am now on a 7440 as other people on campus said they are pretty solid devices.  Still have the issue even after running through the same motions.

I also support maybe 60 people and there desktops and I am beginning to notice that the people that have their 2nd monitor plugged into the HDMI port are having the same issue.  I usually solve the issue by moving the connection over to DP or a usb adapter and never hear about it again.  I believe it is the output from the HDMI port on the computer that has the fault.  I can not find anything that deals with just the HDMI in regards to drivers ... etc. 

Any suggestions or knowledge will appreciated.  Thanks