this worked before:
Go to Edit menu > Preference > Performance.
After it, increase the let Photoshop use to 1504 or 100% by moving the sliders below the box. Then, click OK.
Hope, it is fixed!
Ok so place an INTEGER value in the range. How much ram do you have, multiply by 1024, and subtract 1024 from that nunber. Viola, you have thrown all but 1gb of RAM at the application.
If the first number doesnt come to over 8192, then you dont have enough physical RAM to perform the processing! Easy as that!