narqelion wrote:drathbun wrote:People don't join (or leave) a site based on the tool in use.
Beg to differ but from personal experience, yes they do.

I know I do myself and the same thing happened when I converted a phpBB2 board to 3.0.4 last December for one of my friends. The board had been established for four years on v2, was very active and they positively revolted after I converted.
Fair enough, real-world experience trumps opinion.
It sounds like the switch was not managed very well. I suspect that the board owner simply took it upon himself (or herself) to upgrade without asking any of the board members, or without doing any testing or preview work. For example, I have a long-running board still running phpbb2. I have installed a phpBB3 board running in parallel with a small set of data and invited a subset of users over to test it out. The test users include all of my moderators and a small set of regular "power users" who I trust to give a reasonable opinion. The decision to upgrade... when to upgrade, and how to upgrade... of these decisions will be made by the group and not by an individual. So far the decision has been to wait until we (and by "we" I mean "me") can recreate some of the customizations we have for our current board on the phpBB3 framework.
I am also giving it some additional thought based on
this discussion that took place earlier.
Finally, back to the original poster: the easiest way to undo the conversion from phpBB3 to phpBB2 is to restore your backups. You do have backups, right?

I recognize that if the board has been running phpBB3 for some time that some posts might be lost. However, it sounds like many of the posts from after the conversion were from people complaining about the conversion. It might be worth restoring the code and database backups from before the conversion and trying to rebuild from there.
If it were really important, you might be able to get someone to help with converting the new data from phpBB3 back to phpBB2, but I doubt you will find an official converter. It's too much work to write something that only a few people would be interested in using.