For the Orion web page, if site in IIS was tied specifically to the old IP address (instead of All Unassigned), that would probably cause you problems getting to the web console.
For your statistics collection, it could be an ACL issue. We have ACLs on our devices that define what IPs or subnets can poll snmp data. If the new subnet isn't in your ACL, Orion won't be able to poll the statistical data from your devices.
Your snmp-server community statement will look something like this if you have an ACL on it (assuming you're looking at a Cisco device)
snmp-server community public RO ## (## of your access list)
Your ACL will be something like: (again, assuming a Cisco config)
access-list ## permit 10.2.2.5
access list ## permit 10.1.1.0 0.0.0.255
Hope this helps.
Run the config wizard and the Monitor Polling Engines utility to be sure the Orion server and polling engine are proper.