I think I already answered your post on Steam Community
, but below is my answer again. I'll also add that you can also send the save files to us at Support[at]Frozenbyte[dot]com, but I think you could try the following first. If you email us, please link one of the threads you posted, so we know it's you.
Is the problem still occurring? Also are you sure your Wizard's skills are updated? You can see the skill levels right after pressing the tab key, or other key assigned for the Skills Menu.
If there seems to be a problem with this, you could also try to verify the game cache for the game, in case the problem is there. You can do this by following the instructions below.
right-click on Trine in your Steam Library → click on Properties → choose the local files tab → click the button to verify integrity of game cache
If above didn't help, you could also try to move the item to another character and then move it back to the Wizard's inventory. Did this help?
Let me know how it goes. Cheers!