Research:WestGrid:Reprocessing: sam cannot find the name zhiyil

When I submit jobs (d0 data p20 reprocessing) to westgrid, once my keberos expired, I have to type my password again to re-create keberos certificate. However, even I type correct password, I was still given the following error: zhiyil cannot be found.

The solution should be:
kdestroy
and
remove the file /tmp/PROXY_zhiyil

But sometimes they are not working. Confused....
==============
Traceback (most recent call last):
File "/export/D0_products/ups/prd/jim_client/NULL/v3_0_1/bin/samg", line 179, in ?
sys.exit(main(sys.argv))
File "/export/D0_products/ups/prd/jim_client/NULL/v3_0_1/bin/samg", line 175, in main
command_function(arguments)
File "samg_submit.py", line 262, in samg_submit
File "samg_submit.py", line 133, in translate
File "samg_submit.py", line 157, in translateDoc
File "/export/D0_products/ups/prd/jim_client/NULL/v3_0_1/lib/jim_client/mergejob.py", line 862, in checkSemantic
samgjob.Doc.checkSemantic(self)
File "/home/parag/wspace/samgrid/V7/JIMSUITE/jim_client/lib/jim_client/samgjob.py", line 828, in checkSemantic
File "/export/D0_products/ups/prd/jim_client/NULL/v3_0_1/lib/jim_client/mergejob.py", line 887, in createAttribute
attr = Attribute.factory(token, self.context)
File "/export/D0_products/ups/prd/jim_client/NULL/v3_0_1/lib/jim_client/mergejob.py", line 515, in factory
newDefname,snapId=context.createDatasetfromDimension(tokenValue)
File "/export/D0_products/ups/prd/jim_client/NULL/v3_0_1/lib/jim_client/mergejob.py", line 326, in createDatasetfromDimension
sam_user = jim_client_util.getUserName()
File "/home/parag/wspace/samgrid/V7/JIMSUITE/jim_client/lib/jim_client/jim_client_util.py", line 177, in getUserName
File "sam_common_pylibSamCommand/BlessedCommandInterfacePlaceHolder.py", line 81, in __call__
File "sam_common_pylibSamCommand/CommandInterface.py", line 251, in __call__
File "sam_common_pylibSamCommand/SamCommandInterface.py", line 243, in apiWrapper
File "sam_user_pyapi/src/samUtility.py", line 317, in implementation
File "sam_common_pylibSamCorba/SamServerProxy.py", line 257, in _callRemoteMethod
File "sam_common_pylibSamCorba/SamServerProxyRetryHandler.py", line 266, in handleCall
SamException.SamExceptions.PersonNotFound: GridSubject with name '/DC=gov/DC=fnal/O=Fermilab/OU=People/CN=Zhiyi Liu/USERID=zhiyil' not found.