I have now managed to add the Cisco device but it is showing its last poll as 'never'.
It does however show the traffic in & out and also reports that its online.
P.s. I added these by clicking 'Edit' in 'NetFlow Sources' and changed the drop down to 'Cisco devices only'.
Have you configured NetFlow on the devices? The server won't send netflow but will show up as an endpoint.
Here are a couple of good resources for accomplishing that.
Fot NetFlow in general - http://support.solarwinds.com/kbase/ProblemDetail.cfm?ID=1264