For my fellow HSTers who are also IT guys,
Here's some narrative of what I've gathered so far. Maybe after reading this you'll be able to give me some insight that would help crack this case.
1.) At first, I thought this was a simple script error between the lines that wrote to the table, and the line that will redirect the user. Pretty reasonable assumption. Unfortunately, this doesn't account for the other errors (like those in the Admin and Mod Control Panel). And I tried "elimination" of various blocks of code between the method that actually inserts the post into the database (yes, not just lines, blocks of code, it's a little more complex) and the redirect lines. No go. There are dozens of subroutines in the code, and each sub also calls on a lot of subs or methods, which in turn calls on other subs or methods (it's like a web of daisychains, it will take a few days of concentrated work to trace each "path" in the web, so I'm hoping I don't have to resort to that), so it is still possible to be a script error. It just seems highly unlikely now, though.
2.) In the control panels, the drop down lists (which should have contained data from the database - like forum names, table names, etc.) don't have any content at all. This tells us it's either script, or something wrong with the database or (highly unlikely) the database connection. My bet is still the script. Perhaps looking for wrong table/field names, but they suppressed/silenced the errors for a production environment? I don't quite buy this though.
3.) Those who still use Perl to develop web apps right now may help me with this one. Is it just ikonboard, or is the Perl syntax " = q!myPassword!" really doesn't work for setting a password to a database? This sounds like a stupid question, but whatever is entered there ISN'T accepted by the database, so it rejects the connection (I tried on my laptop.) So those who understand will ask me now - "In that case, how in the hell do we get to connect to the db so that our posts go through, which they do?" Well, the thing is, what is actually written in "q! !" is different from the password listed by the hosting company. Is this standard for Perl in web apps (I don't see why it would be), or, more likely, is this just some ikonboard thing? Perhaps I've missed a subroutine that actually decodes the string so that it becomes equal to the actual password?
4.) There are thousands of Ikonboard forums all around the net, or so I've read. All our troubles happened after an upgrade - which is strange since hundreds or thousands of other sites must have done that too, googling our symptoms don't produce relevant results ("server error 500" and the like get a lot of results, but none that actually resembles our problems). So why is it that we seem to be a solitary case where one routine upgrade results in weird errors?
5.) If I made sense, I would ask you to pm me for whatever IT-guru insights you get in the problem, but since our PMs also don't work, please just post here, I monitor this thread for bug reports anyway.
There's still a ton of stuff I need to sort, compare, study and test. If my test on tuesday succeeds, then I guess that's great, but I doubt it would be that easy. Any insight you can give may mean a faster resoluion of this problem.
Thanks.
-JV