timo There is no update for Diarium available for me in the store (Australia), unless there's a secret method of access I don't know about. It just says Open.
I might have had this problem start after I updated Windows or Excel. I don't copy and paste every time so I don't know when it started. If it helps, Excel version is Version 2405 (Build 17628.20110) which I can see is out of date, I am going to update that and see if it changed anything.
Edit: that didn't change things.