Strange highload on server

Hello,

We have been running our database server without any problem or reboot at
all for a year. Yesterday we needed to change servers so we went ahead and
installed the same postgresql version (8.2.1), restored the database files,
ran some tests offline. Everything was good. As soon as we launch the site
and the traffic hits the server, the load is going up to the sky, and the
top command lists nothing but postgres processes. Strangely, even if i kill
Apache and stop the traffic, somehow the load doesnt cool down, so i thought
this might be an issue with postgres processes not timing out or something.
But we use a very minimal config and the same config was being used in our
other server without any problem.

Server Details:
Dual Intel Xeon 3.20
6 GB Ram
RHEL 4
2.6.9-67.0.22.ELsm x86_64 x86_64 x86_64 GNU/Linux

postgresql.conf
listen_addresses = '192.168.100.58' # what IP
address(es) to listen on;
port = 5432 # (change requires restart)
max_connections = 250 # (change requires restart)
shared_buffers = 20MB
max_fsm_pages = 153600
Other values default mostly.

I tried to increase shared buffers, but kernel didnt allow me. And since it
was working fine with the exact settings in the other server, which is
pretty similar (Dual Opteron 270 / 6 GB ram / Rhel 4). I didnt wanna mess it
up really.

During the high load spike, pg_stat_activity shows dozens of queries from
the site, and i cant really investigate it, cause it spikes up so fast and
if we dont kill the postgres, it goes up to a load of 200 easily.

Any ideas what may be causing this?

Thank you for your replies

Aras Angelo