Uh, yea, my typo (in the post, not the config).
As it turns out, it never should have been working in the first place. We worked on it till the wee hours of the night, and the solution turned out to be as strange as it having been working in the first place.
The history (just in case another sad SA has to tackle this thing at some point):
This configuration at the onset worked perfectly:
(sans things I don't want to share...)
Very soon after successfully testing this configuration, we began sending traffic to this working config and then suddenly one day, PASV suddenly stopped working. As we had no control over the network any longer (our small company was acquired by a large corporation), certain changes and restrictions were made to the firewall, which made it necessary to add the PASV ranges, and strangely enough, remove the pasv_address= declaration. This should not have worked
, but it did for some reason. Like I said, there are definitely things outside my control which appear to change, though the network guys will always claim that no changes had been made.
At any rate, we removed the load-balancer from the equation to eliminate the possibility of it mangling the packets and whatnot, but this didn't prove to do any good, so I set the config back to the original, and what do you know; it works again.
So that is my saga of how VSFTP+Corporate Networks == Shiat-That-Makes-Me-Pull-All-Nighters.