UBB.threads PHP Forum Software Community Forums UBB.threads 6 Version 6 Support Fatal error: Cannot re-assign $this

It sounds like your host has upgraded to PHP5 and your running something like 6.4 or prior which wasn't PHP5 compliant.

The only option to fix is either get your host to move you to a box that's still running PHP4, or do an upgrade so you can run properly under PHP5.