Contact your webhost, inquire as to the last updates they've made to the server you're hosting on. They likely upgraded PHP and a number of items; keeping system software up to date is common, breaking things is also common (an example would be UBB.threads is completely unable to be run on PHP7, which is becoming a common build of PHP).
There is very little we can do to aid in system issues, and all we can really do with a lot of software issues is suggest running a current build as bugs are fixed in incremental builds (plus, this is a user to user support forum and we only support current builds; Isaac and I are contractors, we do not own or otherwise work for UBB.threads).
