>So just last night, I decided to hit "Check For Updates" and there was an update to the new 5.1 update. After I did this, my key commands >began to work again inside of Melodyne. So you should be in Studio One 18.104.22.168815 and that should do it. Give it a try.
I'm having the same problem. Spent an hour editing, then reopened Studio One later in the day to continue and wanted to undo an edit. The first try did nothing, the second try made Melodyne disappear, along with all the work I did earlier in the day...very frustrating.
I would think there should be some sort of fix from Melodyne, and not so much Presonus. I filled out a Melodyne Support Form help request and will be curious to see what they come back with. I'm using Presonus 4.6, and would rather not have to spend more $$$ to upgrade to version 5, being as most of the new features I don't need...plus it would create yet another learning curve that would take even more of what little time I have to devote to music.