I was coming across the same issue and nobody seems to know what to do. Very annoying that Adobe has no answers for this nonsense. What helped me out and actually improved Photoshop's overall performance was go into your preferences, graphics processor settings and click the advanced settings tab, then where it says drawing mode set it to either basic or normal. I had mine set on advanced, which really uses your gpu "intensively." When I did that and set my memory usage back down to 70%, everything returned to normal. Now, I just want to let you know, I have a pretty nice rig too -- gtx 970, i7 quadcore with 24 gigs of DDr3 ram and 3 high speed scratch disks so I didn't think for a second bumping my specs up would cause so many problems. But this is Adobe we're talking about, so two steps forward three steps back is generally the case with them. I actually really miss the stability of CS3. Oh well, try it out, see if it works for you. I hope it does.
A little background:
I saw this problem several times in the past. When I was Beta Testing CS6 many people had similar problems.
In each case, it was the video card driver that was the fix. CS6 beta was being turned out on a weekly basis and all the video card companies were 1 step behind.
There were new video card drivers and new beta versions of CS6 about every 7-10 days there for a while.
During that period, many people saw not enough memory problems and ultimately were fixed by the driver and or Photoshop fixing bugs at a pretty fast clip.
Certainly oddkin and Shadimatar have tons of resources, but if the driver is faulty, you just need a new driver.
Just an observation.