was the dsm-520 hooked up to the tv with hdmi or s-video cable prior to the update?
if s-video, thats the probem [prior to the update mine worked no matter which output is cable is chosen]
after the update u have to go connection by connection [meaning hdmi to hdmi or s-v to s-v and so on]
if u dont have a free hdmi input open on ur tv u r out of luck. if this dont make sense, call d-link and cuss, hopefully they will cave and send u a new one. if that fails, return it.