Basically, more often than not, there's no (None) item in the Item Override in the properties for Current Item and it overwrites whatever Item I was modifying (usually to Amulet 1 in my case).
Sometimes (None) is in there, most of the time not. It's highly annoying when you just need to move an item over and this thing acts up.
I can provide a quest if it's really needed, but it's pretty much random if it's in there or not.
This is in Beta 18 as well
I too have been experiencing this problem.
I don't know if this means anything, but I transferred my quest to a Vista computer and (None) appears on there (same ZC version), but it still doesn't appear on my other computer which is a Windows 7.
All right, got it.
For the sake of testing, you can trigger this by editing a DMap. Opening the item editor should fix it. Basically, there's just one item list, and if the last thing that used it didn't display (None), it won't show up in the override list.
This appears to be fixed in RC1.