pg_dump not working

[Bineeta Guha <bineetag@xxxxxxxxx>]

When I used pg_dump then after few minutes it shows error 

This probably means the server terminated abnormally         before or while processing the request. pg_dump: The command was: FETCH 100 FROM _pg_dump_cursor

Before 2 month backup running normal. But few month Backup only done 869Mb after disconnect auctomatically.

Even I stop all connections still server treminate itself. 

What to do ? Please help me
-- 
Bineeta Guharoy