[Samba] mount.cifs return code = -128

[Winkel, Richard J.]

Could someone tell me what this return code means?  This is mount.cifs 
version 4.8.1 on a
centos 6.4 workstation joined to an AD domain, using automount with 
auto.cifs containing
* -fstype=cifs,sec=krb5,user=&,uid=$UID,gid=$GID,cruid=$UID,noserverino 
://server.address.edu/&

When the machine is freshly booted, and for awhile afterwards, domain 
accounts can mount with no problem.
But after some period of time, maybe day or so, the mount fails with the 
above error.   Rebooting fixes it.
Has anyone ever seen this before?  I don't see how any combination of 
the error codes listed in mount.h could
generate this number.

Thanks for any help!

Rich