These are the things I can think of...
Do you have some firewall software running on the remote server or is there a firewall inbetween the two machines that could be blocking SNMP traffic in one direction?
Do you have entries in your /etc/hosts.allow or /etc/hosts.deny files on the target machine that could be blocking the traffic?
Check the community string to make sure it's correct.
Can you ping the target server from the other machine? If not, there could be routing issue.Ping failures could also be due to firewalls, you'll have to check that too.