While showing the item with Ausir I was able to equip it, not sure about the "trick" but can try to check later.
What is true is that I know that the character i was showing it too wasn't able to use it . This was Samantha Manse, a halfling sorcerer , I thougth that the issue would be the weapon size, since being a 2-handed staff would'n be able to be used by a halfer.
@Dezza Could you let us know the race and the class with whom you tried to pick it up? or its just the charge that doesn't work ?