error while working with pgsql in php

while working with pgsql in php:

Warning: pg_exec() [function.pg-exec]: Query failed: FATAL 1: This connection has been terminated by the administrator. server closed the connection unexpectedly This probably means the server terminated abnormally before or while processing the request. . in db_pgsql.inc on line 67
Database error: Invalid SQL: select * from active_sessions where sessid = 'd320c54bf6502e7609804043d5f29bcd'
PostgreSQL Error: 1 (FATAL 1: This connection has been terminated by the administrator. server closed the connection unexpectedly This probably means the server terminated abnormally before or while processing the request. )

server log shows nothing. second try of execution of php page is succeeding (executing the same query).

Agri