SSH hanging

Hello all,

I'm facing a new kind of problem with SSH
(OpenSSH_3.1p1, SSH protocols 1.5/2.0, OpenSSL
0x0090602f) . I have a Linux 7.2 system with firewall
(iptables v1.2.5). Previously it was accepting
connection from other ips. But Now i'm able to connect
to the system. But I'm able to see only small outputs
(like ls, cat/less small files). If i'm trying to see
large outputs the ssh session hangs forever (like ls
-al cat /var/log/messages). What may be went wrong ?.
I tried reinstalling the entier system. Still the
problem exists. kindly point me some documents/ a way
to solve this problem

This is not only happening to SSH, it occures for all the outgoing
Mail/SSL and incomming Web requests

Thanks in advance

Regards,
a.Johnson