pg_dumpall in post

Hi People

I'm planning to upgrade postgresql version 7.0 to 7.1. I tried backuping of my databases using pg_dumpall > filename.dump. I'm getting the error as follows:

"failed sanity check, table user_details was not found
pg_dump failed on users, exiting"

I couldn't find solution for this problem any where. I need to know how to fix this problem. This has been dragging for  a month. 
Any immediate solution will be appreciated. 

Regards
karthi