Vostro 3460 - standy by issue

My Vostro 3460 has recently developed a annoying issue.

About 1 or 2 a week it will not go into stand by properly. that is, I will leave the machine and usually after about 10 minutes it will go into standy by mode, when I come back I press the power button and the laptop comes back to life.

Well what happens sometimes now is that I come back to my desk and the screen has dimmed (which is okay) when I wiggle the mouse, the screen comes back on, but I can't do anything. using Ctrl-Alt-Del does nothing. Alt-F4 does nothing. using fn+ does some things (like turning on or off the wireless). I can move windows around, but I can't close the apps down.  All I can do is press and hold the power button and reboot.

It does this about one or twice a week.

Previously I had a video issue where once a week I would get a blue screen. But this seems to have gone away with a BIOS update - or a driver update. Hard to tell with intermittent issues!

I have a Vostro 3460, 8 Gig Ram, 1TB Disk. (I upgraded the memory and disk myself)

I have done a full thorough diagnostic from the F12 key on boot. nothing turned up there.

I can only think its a device driver. I have had issue with the Intel Management Engine Inteface Driver..it doesn't seem to install properly. Though when I look at the driver in the Device Manager I can see it installed.

Any ideas what is going on. How I can diagnose which device and driver is causing this issue. 

Thanks.