Belkin F5D8055 v2 not working in native N mode

Is anyone else using the Belkin F5D8055 adapter and having trouble getting it to connect to an 802.11n only network?  I’ve had the same problem with both a Netgear WNR3500 v1 with it’s factory firmware and a Linksys WRT320N using DD-WRT firmware.  As soon as I config for mixed mode, I connect but throughput is marginal at 2.0 MB - 2.5 MB.