Lightroom :: Cannot Import From NFS Directory - Tree Not Expandable

I am using Lightroom 4.3 on Mac OS X Mountain Lion (10.8.1).
 
I am unable to import files from an NFS-mounted directory because the folders lack rocker nodes, so I can't navigate through the tree to my existing Photos directory.  It isn't practical or desirable to import the entire NFS filesystem.
 
I originally had the filesystem mounted with these options:

freenas:/mnt/vol_home/nfs_home on /Volumes/home (nfs, nodev, nosuid, automounted, nobrowse)
 
And while I can see the root of the filesystem in the left side of the import window, and while the directories have little folder icons next to them, the little triangular rockers next to them are greyed out.  If I picked a directory, and checked "include subfolders", then Lightroom would recurse through the tree and show me all of the pictures.  But I don't want to import my entire filesystem.  I need to navigate down the tree to my photo directory, but the rockers are "greyed out".  It's difficult to see them greyed out when the background is grey too, but they are there, faint as they are.
 
So, I thought maybe the "nobrowse" option had something to do with the inability to navigate.  I used "NFS Utility" to remove the "nobrowse"option, and remounted the filesystem.  It is now mounted with these options:

freenas:/mnt/vol_home/nfs_home on /Volumes/home (nfs, nodev, nosuid, noatime)
 
And while I can see the root of the filesystem in the left side of the import window, and while the directories have little folder icons next to them, [most of] the rockers next to them are still greyed out.  Here is a screenshot of the import window, alongside a Finder window, which of course lets me open the rockers and navigate just fine.  The fact that Finder works implies to me that it isn't a permissions problem.  Of course I can also "cd" using the terminal commandline.  The navigation problem appears to be limited to the Lightroom application.
  
only the "rbrown" folder has a working rocker.  The other rockers are greyed out (which is really difficult to see).  I need to navigate below "rbrown", but cannot.   Finder can open the "family" rocker, and can open the subfolders under "rbrown" just fine.
 
Why does lightroom refuse to let me open these folders?