So I did a clean XF1.4.5 install and started to import the conversion (which is in 1.4.5). When I go to import threads, it gets to 94.33% (about 8-9 minutes in) and then I get "Error. Please enter a valid value."
I've looked at the xf_post table and discovered some weird conversion errors that resulted in photos being translated into text (tens of thousands of characters long) and manually deleted the content of those posts out of the table. That didn't do it.
I haven't looked at the xf_thread table but I suppose I should, to see where it stops. I'm guessing there is an invalid post title or some invalid post content that is causing the import to error out. Otherwise, the import seems to be fixing the issue I was trying to avoid fixing manually, and also since this is causing this error now, it is potentially relieving an future issue...so it's a good thing I tried it.
Any insight as to what might be causing this error or where to look would be appreciated.
I have no errors in the server log.