Sorry to hear that the 4520 is defective . It is frustrating especially since you when through all the work of moving the 4311 to another room. Then to take the time to set both units up only to find the 4520 is defective. Well the good thing is you have the 4311 to fall back on which is nice to have. I'll be interested to see if you get another 4520 or not.
Bill, I returned the 4520 for a refund, and have decided to wait awhile before considering getting another 4520. I paid MSRP, so I am likely to wait until some discounts start appearing.