UBB.threads PHP Forum Software Community Forums UBB.threads 6 Version 6 Support array_keys(): The first argument should be an array

Hey guys,

I've converted an OLD, OLD (v4.4) wwwthreads message board to 6.4.4. All of the posts, etc, and features work, except I get the error below, only on imported (imported via alter tables) threads that have zero replies. New posts with 0 replies do not get the warning. This also only happens when a user is looking at the post in threaded mode. Any hints/tips?

(obscured the path purposefully)

Warning: array_keys(): The first argument should be an array in /path/to/boards/showthreaded.php on line 97

The line is:
$parentkeys = array_keys($tree[$currentkey]);