Doh!
It would have helped if you had said you were not running the new version of nUI yet. If you've applied for access to the nUI+ User Group as per the newsletter instructions, you should have access to the download area now.
As the announcement clearly states (highlighted in yellow)...
Note that as of this morning's WoW 3.1 patch, nUI Release and nUI+ Release are both broken. nUI+ PTR Beta and nUI+ Development are the only versions that will run on the new WoW patch.
http://www.wowinterface.com/forums/s...ad.php?t=22095