PC going into black screen when resuming from sleep mode. Win 7 64

[David_647]

So, after getting hit with a huge electricity bill I figured running my pc 24/7 wasn't the wisest.
So I figured sleep mode would be the best when not using it.
Problem is that sometimes (maybe 50%) the computer will not fully wake from sleep mode.
The PC switches on and either goes straight to a black screen or a blinking cursor.
I can restart the PC by holding the power button in and it goes back to system resume; I can see system resume on screen and my keyboard lights up (Logitech G19), then the keyboard lights go out and I'm back to a black screen/blinking cursor (like the "ready to type" one in command prompt), I can then shut the computer down again and I get the option to delete restart data and reboot or retry; which hasn't worked so far.
I did notice, once that when I left the house for about twenty minutes with the cursor blinking my keyboard and mouse had "woken up" and a few minutes later, so did the PC.

It doesn't happen all the time either, maybe half the time it restarts instantly.

Any idea of what could be causing this and how to fix it. System restore won't work as I have no idea when this started.

 

[David_647]

So far I've tried installing the latest graphics driver's for my RX-480, which made things worse; I got multicolor static/fuzz until the PC booted which meant I couldn't access safe mode, the BIOS etc.
Fixed it by uninstalling and reinstalling the drivers, but the latest drivers are definitely more prone to fault than the old ones.

I've also noticed that if I hard reset the PC during the first black screen then wait with the second one with the flashing cursor, the cursor will eventually go away and the computer will boot up very slowly, blackscreening and returning to normal multiple times. I'm certain this is related with my graphics card as I run my setup through an AVR, when blackscreening the HDMI light goes out, as do all the speaker input (essentially the AVR shows whether it's receiving 2.1, 5.1 or 7.1 audio with icons of the speakers) icons, the HDMI light and icons then come back on intermittently until I go to "switch user" (from ctrl alt del) which seems to reset the graphics drivers.

Can anyone please help, this is driving me nuts. your help would be much appreciated.