What version of Net::SNMP are you using? RPMFind has it as an RPM package at version 5.4.1-6fc8 as the latest version, but there's an earlier version listed. The newest I found on CPAN is 5.2.0, though.

I know this is an odd question, but do you have IPv4 enabled on your new server, or only IPv6? Another odd one for you -- can your web server open a UDP socket under either? Is there an application-level firewall involved?

When I rigged up the missing parts of your program quickly, I got the message about not being able to communicate with the device. That's expected, since I pointed it to a device with no SNMP server running. I didn't get any errors about permission denied or any other session-related errors. I'm running 5.10.0 with Net::SNMP 5.2.0 on Mandriva 2008.