Here's an update to this situation . . .
I should have mentioned previously that my V500 (and 5 other devices) are plugged into a Belkin 7-port hub. While there's no mention anywhere that this scanner may not work on a hub, I've been successfully scanning for more than 2 years and a couple of MacOS updates, and as a result, I didn't even think this would have been a problem.
I made another call to Epson, and their rep had me do several troubleshooting tasks. Based on the results, he deduced that there was a hardware failure. This is not what I wanted to hear, and quite confusing given it had worked fine up until the 10.8 upgrade.
While I was on the phone waiting for the rep to talk to his 2nd-level support, I thought about one more possibility: hook it directly to my iMac. So I unraveled all my USB peripheral cables, and put the Epson's cable into one of the iMac's USB ports on the back. Then I re-installed the v3.74 Epson Scan software (this is "epson13659.dmg" off their site) and the latest VueScan v9.1.14 and crossed my fingers. ;^) I started up Image Capture - no problem setting the dpi or adjusting the crop window (previous problems) - it scanned just fine! Then I tried Epson Scan - again, no problems whatsoever! Finally, I ran VueScan - everything worked exactly as it had in previous releases! Wow . . .
So I don't know what to make of this other than the scanner now seems to require being directly attached to your computer's USB port. Maybe it's the length of the signal path through the hub that's just a little bit longer, or maybe the hub's signal strength is just a bit lower.
@lyndhurst, I don't know if this is similar to your situation, but if it is, give this a try . . .
Hope this helps other people . . . And I take back all those negative comments about Epson software. ;^)