Like Isaac said, it sounds like your database is expecting the data to be in one format, but the forums are presenting it in iso-8859-1; more recent versions of UBB.threads (namely v7.6.0) fixes quite a lot of problems over past releases.
If you look at the
UBBWiki posting "
UBB.Threads Changelog Index", you're running v7.5.5 (February 10th, 2010) whereas the latest is v7.6.0 (February 15th, 2017). There have been a vast number of improvements over the 7 year span since your version was released (if you click on a release it'll show you the developer notes).