I don't have a link handy, but the report I heard was that they had corrupted their database (the GOP that is).  So that when they tried to mail all these new registrations, they weren't mailing to real addresses.

ex
Joe Q Public      Jane R Adem
123 Main St.      123 High St
Anytown, USA      Americantown, USA
11111             11211

Were getting mingled and was printing things like

Joe Q Public
123 High St
Anytown, USA
11211

So the addresses and zips were failing and the post office sent them back.  This was the report on what I heard about why the one court had thrown so many of their challenges out.