Bug
https://bugzilla.zimbra.com/show_bug.cgi?id=39549 "ZimbraDnD not compatible with FF 3.5 & GnR" was marked as a duplicate of
https://bugzilla.zimbra.com/show_bug.cgi?id=24797 "DnD Zimlet need to take advantage of new compose window" which was set as fixed. This doesn't look logical for me. There is also
Bug 27153 – DnD plugin : Multi-Browser/Platform "DnD plugin : Multi-Browser/Platform".
Now, I don't know what the appropriate bug for ZimbraDND in Firefox 3.6 would be, but I'd like to have a single RFE to vote for.
EDIT:
https://bugzilla.zimbra.com/show_bug.cgi?id=44828 seems to be that one.