hmmm...
ok.
well, having no idea what is downstream in your mcl, it is tough to say, but...
a lightning strike/surge, etc... *may* have caused the initial issues w/ the 7000 and likely down the mcl to additional components, as it sounds now.
are you running mcl2a's or a/v's? w/ an a/v you should be able to at least plug an aux source in at the link room locale (say a cd unit) and see if you have any ouput in that room. if you have the a's -maybe someone else might have a test???