When I attempt to merge, I get the error message:
Fatal error: Unsupported operand types in /mnt/raid1/shares/drupal-6-PQ-616/includes/common.inc on line 2891
This does NOT occur when I merge by clicking terms in the tree and entering a new term for the merged survivor. It occurs when I first SEARCH for a term to be merged, find it and display same to the right of the tree, then click on the merge button, and then enter the new term for the merged survivor.
The reason that I do NOT use the tree to select the term to be merged is that I have a concept tagging taxonomy of over 20,000 terms. Scrolling and paging is very time consuming and difficult.
There is a possibility that the merge was never intended to be made by first using the search, but I found nothing in the documentation on this point.
Other than that, the module is great and I use it constantly.