MacBook Pro retina wakes to black or grey screen

Hi all, my 9 month old rMBP has started to wake from sleep to a black or grey screen and I have to force close the system and restart to get a usable desktop back.
It started about a week ago when it woke to a grey screen (like the background when you re-install the system). That happened a few times but in the last day or so it has started to resume to a black screen.
This only happens after it's been asleep for a few hours. If it only sleeps for half an hour it's fine.

I think I'll try a re-install and see if that cures it.
Any other suggestions?
Thanks.

Well I re-installed ML and it cured things for a few days.
Sadly now it's worse!
It now doesn't wake at all. It's absolutely dead when I try to wake it up from a sleep of a few hours.
No sign of life at all, no keyboard light, no screen backlight.
If I press and release the power button nothing happens at all.
All I can do is do a hard shutdown and then boot from cold - which works fine.

I phoned Applecare who told me to reset SMC and PRAM (I think it was) and they opened a case number in case that doesn't solve the issue.

Should I be looking at anything else?
Thanks.

If resetting the SMC and PRAM does not resolve the problem, it's probably time to make an appointment with your local Apple Store genius bar.

Ok I'll do that after keeping an eye on things for a day or two.
Thanks chscag.

Well it seems the problem is solved but in an unexpected way.

I have uninstalled rEFInd and my problems have gone away!
I have OSX, Windows 8 and Ubuntu 13-04 (both EFI booting) so I installed rEFInd boot manager to get those pretty little icons at startup (and to get rid of one of the screens shown by EFI Boot in the Alt+boot screen).
When refind is installed I get the problem. When refind is uninstalled the waking from sleep problem disappears.

I have conversed with the maintainer of refind and he informs me that a small number of people have already reported this problem to him. It seems that it can happen with later Mac's.
I'm hoping a fix can be worked out as I quite like refind and would like to start using it again.
Anyway, for the moment refind is uninstalled and things are fine.

Thanks for posting back. Instead of using rEFInd, why don't you try rEFIt instead? It's bug free as far as I know and it's also freeware. And yes, it gives you those pretty icons on startup!

Download LINK

Thanks chscag.
I thought about refit (and indeed may give it a try) however, refind is a modern fork of refit and refit hasn't been maintained for a number of years now.

chscag, I've installed refit and no grey/black screen on wakeup so far

OK, great. I've been using rEFIt for years (I know development has stopped) and it just works. It's easy to install and remove. It was a bit hard at first to get its configuration file going the way I like but after a lot of experimenting and reboots, I was successful.

chscag said:

OK, great. I've been using rEFIt for years (I know development has stopped) and it just works. It's easy to install and remove. It was a bit hard at first to get its configuration file going the way I like but after a lot of experimenting and reboots, I was successful.

Click to expand...

Yeah, I haven't actually configured it yet, it's sort of running as it came
I would like to get rid of some of its menu entries though if you have any suggestions. The refit config page seems a bit fuzzy
Thanks again.

EDIT
actually chscag disregard the above
In order to update to Windows 8.1 I've had to resort to a Bootcamp partition due to graphics driver problems.

For anyone that sees this again, I have a 13" MBP mid 2012, running Yosemite 10.10.3, and I was using rEFIt and got this problem. Didn't try rEFInd, but I am absolutely positive that it is a problem with rEFIt because:
1. When I don't touch any buttons at the black screen, it boots into Ubuntu, which is my default partition to boot into in rEFIt if I had started from cold boot
2. If I "navigate" to the Mac OS X partition using the arrow keys (I know it's the third entry, since it is on the rEFIt menu on startup), and click enter, it wakes correctly to Mac OS X

Not sure if it's a problem in rEFInd as well, but I'm willing to bet since it sounds like other people have this as well, that it is.