Problem after upgrade

[ZiNgA BuRgA]

Okay, take a look at the threadfields table, is there a field named hidefield?

If yes, chances are the upgrader did all the upgrade tasks, but didn't update the version.  In which case, you can manually edit the version number inside cache/xthreads.php to be the new version.  After that, edit any threadfield, then check that cache/xthreads_evalcache.php file exists.

If no, then the upgrader probably broke mid-way, which is going to be problematic.  If you don't mind looking through PHP code, you can open up inc/xthreads/xt_upgrader.php and follow through to see what the upgrader does and revert changes it's made.
Otherwise, it may be easier to back up thread field and forum settings information, uninstall XThreads, then reinstall it.