This is from a walkthru that I found:
In order to hire the new versions of henchmen,
you have to first release the old henchmen, and the game doesn't want you to
do that--the Release button is grayed out when a henchman is selected.
There is a workaround and it involves filling the first page of your party
inventory with pets. Just buy enough pets (at least seven) to fill the first
page of your party inventory and disband them to the Inn. Then go to the Inn
and Add henchmen and disband them until they are all on pages 2 or 3 of the
party inventory. Now, when selected, the Release button should be available
for the henchman.
Remember! Don't release a henchman until you are finished with the game (or
have just started a new game at higher difficulty). Once released, they are
gone forever in the current game.
My personal disclaimer: Before adding the new version of a character make sure they are what you want them to be.. I started off lothar in mercenary as a melee fighter.. but when I went to add the new version of him he was a combat mage.. and I had Deru as a ranger but the new version of her was a nature mage.. I didnt notice either of them at first and boy did it mess me up!!!
[This message has been edited by Baldylocks (edited 03-14-2006 @ 11:11 PM).]