UBB.classic was actually discontinued back in 2006. And an email was sent out to all customers of that several months before that happened. The UBB.classic forums are still here as a courtesy, but the product itself is quite outdated and we don't even have anyone in house anymore that was on the UBB.classic development staff. Most of the time, users that actually ran the product know more about it then anyone that is with Mindraven.
That being said, we do try and offer assistance where we can. In that particular eorr you are getting now I'm not even sure where I can offer assistance. I've even set the search back to 10 years on the forum trying to search for the _open_buffered error you are getting now and nothing at all, so I'm not entirely sure what it is.
When you asked if your data could be transferred to the latest version. It can, but you'd need to upgrade to the latest version of UBB.classic first, which is 6.7.3. And in fact, that's probably what I'd suggest doing.
You might be running an old enough version where you're running into a particular bug or issue, since there were many fixed during the course of UBB.classic. So, what I'd probably do first, is make a backup of everything and then do an upgrade to 6.7.3, which this guide:
https://www.ubbcentral.com/support/docs/ubbclassic/UBB6_upgrade_within_6.html
