A couple of things:
1. There are some more properties that you need to set to make the website happy: set MachineType and VendorIcon to empty string (""). We have a fix for the product that takes care of setting these default values (as well as some other bookkeeping like the IPAddressGUID property), but it hasn't shipped yet.
2. The "PollerType" property needs to be one of the documented values. In this case, you want "N.Status.ICMP.Native".
Hope that helps.