@VJware
Nothing else in the logs.  This is interesting; if I only select the flatfile of the LUN and no snapshots the backup fails.  However, if I select just one snapshot the backup goes through.  Though doing it this way I'm backing up the snaphot and the non-snapshot flatfile of the LUN.

@Colin Weaver
NDMP Option is not the recommended way to backup a LUN as you get no granular visibility within the LUN itself you just get a single large file backed up.
-Completley agree, do you know of a way to backup/mount a LUN within Backup Exec to get that granular visbility?

Admittedly this does not answer your question as it should still backup. However unless you only want complete DR and nothing smaller then you should probably take a look at your overall backup strategy and design.
-I agree it's not ideal, but we have a policy to backup the NetApp filers to tape in case everything goes down in flame.  Even though restoring that amount of data from tape would be beyond time consuming.

Are you actually selecting the LUN for backup or are you trying to select a snapshot of the LUN?
-I've tried both, please see my reply to VJware above.

If you select the whole volume that the LUN resides on does it backup?
-Yes (created a volume that's a LUN on the NetApp).  Meaning the LUN doesn't reside inside an NFS volume.