There has been a lot of changes in the dochangeusergroups.php file from 7.7.4 to the currently unreleased 7.7.5
the following fix should get you back in business:FIND around line 94
$aquery = preg_replace("/t1\./", "", $aquery);
REPLACE WITH
// $aquery = preg_replace("/t1\./", "", $aquery);
This line and the whole section has been unchanged in all prior versions for at least the past 10 years -- since at least 7.5.5 from 2010.
UBB.threads 7.7.5 will have useless code removed and known bugs fixed.
One of those a long time bugs which will be fixed with the release of 7.7.5 is:
member search with CHANGE GROUPS + ALL MEMBERS IN SEARCH
ADD TO: works as expected
REMOVE FROM: does not work
basically, ALL MEMBERS IN SEARCH + REMOVE FROM GROUP does not work for versions 7.7.4 and prior.