DGL-4500 with firmware 1.13. WPA2 Only, AES
2x DWA-160 Adapters running 1.2.2.0 Ralink drivers (09/05/2008) on XP MCE 2005 SP3.
1x Intel 4965AGN running 12.0.4.0 on Vista64.
Chipsets:
AMD/ATI Xpress 200M hosts a DWA-150
Intel 915M hosts a DWA-150
Intel 965M hosts a 4965AGN
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When the DGL-4500 is set to 5GHz N and the 40 channel DWA-160 adapters experience frequent and random disconnects under load. The DGL-4500 log only shows the DWA-160 adapters initializing an associating; never a drop. The Intel 4965AGN adapter handles the situation with no errors.
When the DGL-4500 is set to 5GHz N and the Auto 20/40 channel the DWA-160 adapters experience less frequent and random disconnects under load. The DGL-4500 log only shows the DWA-160 adapters initializing an associating; never a drop. Performance increases moderately versus 40 only. The Intel 4965AGN adapter handles the situation with no errors.
When the DGL-4500 is set to 5GHz N and the 20 channel the DWA-160 adapters experience even less frequent and random disconnects under load, but still eventually fail. The DGL-4500 log only shows the DWA-160 adapters initializing an associating; never a drop. Performance increases slightly versus Auto 20/40 only (and is frankly amazing). The Intel 4965AGN adapter handles the situation with no errors.
When the DGL-4500 is set to 5GHz A, which apparently defaults to the 20 channel, the DWA-160 adapters are rock steady solid and stable. Performance decreases greatly versus any of the previous N selections. The Intel 4965AGN adapter handles the situation with no errors.
I have tried returning/replacing one of the DWA-160 models with the store and found identical behavior so I have no reason to believe the adapters defective.
The DWA-160 disconnection behavior was also experienced on DGL-4500 Firmware before I upgraded. I did not test that scenario as thoroughly.
The DGL-4500 is reporting signal strength of 40 to 60% to all three adapters.
I am unclear on how to proceed from here. Obviously I could simply revert to 5GHz A and have the stability I seek, but the 5GHz N throughput is just stunning and I want it.

None of the hardware seems defective so I am unclear on if this is a software issue with the DGL-4500, the DWA-160 drivers, both, or environmental. Of course all that begs the question why the 4965AGN is behaving so well.