Remote Asistance Failure to Connect

I/we use Live Messenger to consistently have a video conference or Instant
Message with a friend in a different state. I cannot accept a request from
my friend for Remote Assistance. We also tried the email request for RA and
get the same error message. RA Cannot make the connection - The person you
are trying to help might have closed RA. (He did not close anything)

Why would Video Conference work and Remote Assistance not work? He has XP
on a DSL link and I have Vista on a LinkSys VoIP router supplied by Vonage.
--
Stan