BUG #5756: postgres eat up all memory(2GB memory)

The following bug has been logged online:

Bug reference:      5756
Logged by:          amos
Email address:      amosleaf@gmail.com
PostgreSQL version: 8.3
Operating system:   windows server 2008
Description:        postgres eat up all memory(2GB memory)
Details:

Hi:
I am sorry for not good at english, so please be patient with what i write,
I really need your help,thank you in advance.

Current situration:
(1)Our server use postgres8.3 database.
(2)The server would receive 500-1500 http request, and for each request,
server would operate the database once, so may it would use one database
connection.
(3)then I modify the configuration in "postgresql.conf".
What I changed is:
(1)max_connections = 2000
(2)shared_buffers = 32MB
(3)statement_timeout = 1800000  //this is 30 minutes

So the result is: when the server is working with more than 500 request, the
postgres eat up the memory.

BTW, our server is running java program, use a database pool whose name is
"c3p0".

So which configuration should I change to avoid this?
Thanks again!