Problem with juniper ssg 140.

Hello all,
I have a big problem with a firewall juniper ssg 140.

The firewall is updated with the last release software.
It is configured this way: a peer BGP configured with two Cisco
routers 7200 a primary and a secondary, and has eight other locations
with the same firewall connected vpn on it.

When traffic is less than 20MB everything works perfectly, when
traffic exceeds 20MB peer bgp fall continuously.

Another problem even more worrying is that there is no longer able to
reach the firewall.

The management interface is different from the peer bgp.

The cpu utilization when the peer is up and the Firewall isn't reach
for managment is from 3% to 5%!!

The Firewall learn 1000 route from bgp peer.

Thanks in advance for your answers