OpManager not discovering some Cisco devices properly

OpManager not discovering some Cisco devices properly

I'm having issues with Opmanager listed below:

a) Discovers some Cisco devices as Desktops (eg. 3750 Switch, 2800 Router, 7200 Router, 6509 Switch).
b) Does not graph switch/router CPU, backplane and memory usage properly for devices including ones identified as routers/switches.
c) There is a mix of IOS's, ranging from IOS 12.2 to IOS 12.4.

I have tested SNMP credentials to the devices and they work. I have added additional MIBs and performed a manual rediscovery of devices and they are still listed as desktops. Ciscoworks identifies all the devices successfully yet Adventnet doesn't.

Any suggestions to getting this working in Adventnet?

Cheers,
Zig