We've heard that a new version of the Zune Desktop application is required for the upcoming Windows Phone 'NoDo' update and sure enough, an update just went live.
If you go to your Zune Desktop --> Settings --> Software --> General, you can force an update-check to grab v4.7.1404.0--which seems to be the same version as before, so we're unclear of any direct changes.
The new version of Zune Desktop is suppose to allow your Windows Phone to be backed up in preparation for 'NoDo', allowing you roll back if there are any problems during the flash. Of course the bigger news is this probably signifies that the actual Windows Phone update is only days, if not weeks away or that MS is gearing up for some changes in anticipation. (And call us crazy, but Zune seems to load a lot faster now).
Update: Cursory look so far reveals no significant changes besides perfomance. Find anything? Tell us in comments.
Update 2: While the overall version number is the same, two components have changed as noted by reader mparker: ZuneWmdu.dll and ZuneWmduResources.dll are both now v4.7.1407. Microsoft's support page in fact mentions these as needed for the software backup: http://support.microsoft.com/kb/2498092 So this does look like a prep for the 'NoDo' update.
Thanks, David M., for the great observation!