HowTo: get landscape from overcast day look sunnier?

ACR 5.6 PS-CS4

I'm trying to get a group of pictures taken on an overcast day to look more like they were taken on a sunny day. The originals are flat and dull. Here is a sample .dng:
http://www.lynnallan.org/pictures/100329b_055249_PulpitRock.dng

and the generated .jpg from the "As Shot" default ACR settings:

and the generated .jpg from ACR adjustments (contrast, clarity, vibrance, sharpness, saturation, etc.)

I tried a variety of tweaks, but didn't have much success. That included increasing contrast, clarity, vibrance, saturation, sharpening, and a LAB-color move a'la Margulis' "Canyon Conundrum". Still pretty flat.

http://berean.myphotoalbum.com/view_photo.php?set_albumName=album329&id=100329b_055249_pulpitrock

I'd appreciate guidance on what (if anything) can be done in this situation to get a better image.