Here's a quick fix compiled from a couple of Shauno's threads for the tech-challenged (like me) for NextGEN Gallery Voting failure after NextGEN Gallery upgrades. (This is for basic default view only.)
1. Copy Shauno's file from http://pastebin.com/ZbcPeGV0
2. On your host, go to: wp-content>plugins>nextgen-gallery>products>photocrati_nextgen>modules>nextgen_basic_gallery>templates>thumbnails>index.php
3. Erase contents (not file) of index.php and replace with what you copied from pastebin.
4. Clear your cache
If voting still doesn't work on your site you may have to (gulp) delete and reload all your photos.
I followed this process last week after the major NextGEN Gallery update and I did have to reload photos. I had to do it AGAIN today after NextGEN Gallery update to 2.0.33 but fortunately did not have to reload photos this second time around.
There's probably a way to not have to change the file after each NextGEN Gallery update, but that's beyond my skill level. So in the meantime, I plan on NOT updating NextGEN Gallery for a long time. :)
Thanks, Shauno for creating NextGEN Voting.