Hey folks.
I run my Acer monitor off the DVI cable. Used to run dual screen to my TV off my mobo's Intel onboard gfx through HDMI.
Recently ran into an issue with first windows 7 on a clean install on a new SSD drive then Asus drivers not seeing my OS as Win7. (Something to do with MS trying to nerf win 7 imho) anyhow, now I can't use that config until I get that resolved.
Long story short, used the HDMI to mirror my PC to watch a movie recently by simply connecting the cable to the port while in operation. Upon reboot, PC monitor shows bios, etc... but once it loads the drivers for windows screen goes black & monitor reports lost signal. Boot in Safe Mode, all fine. Clean install of latest WHQL drivers from Nvidia, reboot normally. Same issue. Unplug & replug DVI to vid card, & screen is fine. Nothing is now connected to EVGA card HDMI slot & I still get this. 
HDMI to TV never had issues, Just the DVI No clue what unseen setting is loading on normal windows boot, but it seems to be effecting the video card itself since the monitor drops the signal and only picks it up again after physically resetting it.
At least I have a work-around, but would like a more permanent solution.
 
Can't seem to up my dxdiag.txt, so I'll paste the most relevant junk:
 
System Information
------------------
Time of this report: 4/27/2017, 15:01:38
Operating System: Windows 7 Professional 64-bit (6.1, Build 7601) Service Pack 1 (7601.win7sp1_ldr.170307-1800)
BIOS: BIOS Date: 07/21/14 10:57:51 Ver: 25.01
Processor: Intel(R) Core(TM) i5-2500K CPU @ 3.30GHz (4 CPUs), ~3.3GHz
Memory: 8192MB RAM
Available OS Memory: 8134MB RAM
Page File: 2755MB used, 13511MB available
Windows Dir: C:\Windows
DirectX Version: DirectX 11
DX Setup Parameters: Not found
User DPI Setting: 120 DPI (125 percent)
System DPI Setting: 96 DPI (100 percent)
DWM DPI Scaling: Disabled
DxDiag Version: 6.01.7601.17514 32bit Unicode
---------------
Display Devices
---------------
Card name: NVIDIA GeForce GTX 960
Manufacturer: NVIDIA
Chip type: GeForce GTX 960
DAC type: Integrated RAMDAC
Device Key: Enum\PCI\VEN_10DE&DEV_1401&SUBSYS_29663842&REV_A1
Display Memory: 4095 MB
Dedicated Memory: 1969 MB
Shared Memory: 2126 MB
Current Mode: 1920 x 1080 (32 bit) (60Hz)
Monitor Name: Acer H274HL
Monitor Model: Acer H274HL
Monitor Id: ACR0264
Native Mode: 1920 x 1080(p) (60.000Hz)
Output Type: DVI
Driver Name: nvd3dumx.dll,nvwgf2umx.dll,nvwgf2umx.dll,nvd3dum,nvwgf2um,nvwgf2um
Driver File Version: 22.21.0013.8189 (English)
Driver Version: 22.21.13.8189
DDI Version: 11
Driver Model: WDDM 1.1
Driver Attributes: Final Retail
Driver Date/Size: 4/19/2017 21:57:43, 16431504 bytes
WHQL Logo'd: Yes
WHQL Date Stamp:
Device Identifier: {D7B71E3E-5741-11CF-0F44-6B091BC2DB35}
Vendor ID: 0x10DE
Device ID: 0x1401
SubSys ID: 0x29663842
Revision ID: 0x00A1
Driver Strong Name: oem23.inf:NVIDIA_Devices.NTamd64.6.1:Section024:22.21.13.8189:pci\ven_10de&dev_1401
Rank Of Driver: 00E62001

bcavnaugh
Have you done the same test as above but when you remove the DVI cable First Unplug the Power Cable on the Monitor.
Then Plug back in the DVI Cable then the Power Cable and then then turn on the Monitor.
Sounds like your HDMI port on the TV is an Active Port.

The HDMI cable is no longer attached in either direction, went thru full shutdown including cutting off power supply for 1 min. (in case some odd setting was being held in resident memory yada yada.) Display setting shows no second "phantom" monitor..... All works as should, but not until the DVI cable is removed, then re-attached AFTER windows loads. Windows has obviously designated the HDMI port the default for my EVGA card somehow and tells the hardware to ignore other ports. turning monitor on/off is not enough to actually "wake up" the DVI port. I haven't bothered with the monitor power cord, nor do I see a reason to. I'll check thru the finer settings in Device manager, although I already removed it as a hardware item and rebooted leading to "hardware discovery" blah blah. 

krakr_mpf

bcavnaugh
Have you done the same test as above but when you remove the DVI cable First Unplug the Power Cable on the Monitor.
Then Plug back in the DVI Cable then the Power Cable and then then turn on the Monitor.
Sounds like your HDMI port on the TV is an Active Port.

The HDMI cable is no longer attached in either direction, went thru full shutdown including cutting off power supply for 1 min. (in case some odd setting was being held in resident memory yada yada.) Display setting shows no second "phantom" monitor..... All works as should, but not until the DVI cable is removed, then re-attached AFTER windows loads. Windows has obviously designated the HDMI port the default for my EVGA card somehow and tells the hardware to ignore other ports. turning monitor on/off is not enough to actually "wake up" the DVI port. I haven't bothered with the monitor power cord, nor do I see a reason to. I'll check thru the finer settings in Device manager, although I already removed it as a hardware item and rebooted leading to "hardware discovery" blah blah. 

The Power Plug on the Monitor Not the Computer Power Supply.