I was just trying to find a bug related to this problem, and yes I agree the bug titles and the text really aren't worded too well. 39549 was supposedly the bug relating to getting DnD to work with firefox 3.5, and after a fix was checked in it was marked as a duplicate of 24797, which from what I can see isn't really related...
Bug 40996 - DnD plugin/zimlet doesn't work in ZD2 at all which relates to the Zimbra Desktop client version 2 (based on the same framework as GnR I think) is also marked as a duplicate of 24797.
Basically it looks like they are putting all the problems with DnD not working into bug 24797, so if it's going to be fixed that looks to be the place to watch for updates on the situation.