Strangely enough, I upgraded vBulletin to 3.7.3, and Photopost started working a little bit. After going into the database manually and changing some configuration settings (for pathnames), along with some config files I found, I managed to get it mostly functional. But, thumbnails are not displaying.
Do we really
need to update Photopost? The site owner is going to hold off on upgrading for a bit. With
vB at the latest version, our forum is now more secure and running properly. And it looks like Photopost may run just fine...but not knowing the product that well, I have to poke around to figure out more about how it works, and why thumbnails aren't showing up (if they were ever enabled in the first place).