[OpenAFS] rxk error: caller not authorized

[J Maynard Gelinas]

   I'm seeing a strange intermittent problem with clients trying to login 
via gdm at the console. They successfully login, yet are unable to access 
their files stored in AFS. The error message at the client machine reads:

Apr 22 10:43:56 ctppaganini kernel: afs: Tokens for user of AFS id 0 for 
celllns.mit.edu are discarded (rxkad error=19270405)

Which means, according to:

http://grand.central.org/numbers/et/RXK.html

"19270405 RXKADNOAUTH caller not authorized"

   Manual attempts at obtaining a ticket via kinit and aklog
intermittently seem to return a successful result yet lead to "permission
denied" failure when attempting to access files stored in AFS space. 
Re-authenticating then solves the problem. 

   Googling for solutions to this problem has been unsuccessful. Can 
anyone offer insight or a link as to potential causes and fixes?

Thanks,
--Maynard