I'm accessing postmaster through python using the _pg module.  Last night it was working fine.  This morning the database is all messed up. When I do a transaction:

Begin;
Insert ....;
End;

I get errors:

NOTICE:  (transaction aborted): queries ignored until END

Then sometimes I get a notice that there is no connection to the backend even though postmaster is running.

from psql, I tried : 

select * from xml;

I got this error:

pqReadData() -- backend closed the channel unexpectedly.
       This probably means the backend terminated abnormally
       before or while processing the request.
We have lost the connection to the backend, so further processing is impossible.  Terminating.


Any ideas to what could have happened overnight?

Thanks a lot
Brad Marshall