Do you have the adapter selected under Connection Settings in HotSync Manager? Also, (I don't mean to imply you are missing the obvious, but I do this all the time) do you have HotSync enabled in HotSync manager, and do you have "Enable HotSync software at system startup" checked?
I use that exact Keyspan adapter with my Palm V and it has worked like a charm for years. Only problem I've encountered is that every now and then HotSync Manager needs to be "jiggled" (just turn it off and on again).