db sever seems to be dropping connections

I'm facing an issue with PostgreSQL .. The server seems to drop the
connection to my script after a couple of hours (sometimes, not always).

DBD::Pg::db selectrow_array failed: could not receive data from server:
....
....
:server closed the connection unexpectedly.

And in another scenario it failed with the message:
DBD::Pg::db selectrow_array failed: could not receive data from server:
Connection timed out

Is this a known issue? I'm running PG 7.3

--Rushabh Doshi