i do have the same problem...
it took me some hours last night to solve my problem being unable to send messenges to ppl on my contact-list (ppl with yahoo email adresses) and now that i have finaly fixed this i cant see their real status on my desk...
they appear online inside the messenger window and they appear to be offline at my desktop-contacts... last night before i went to bed my father appeared online at my desktop-contacts while i knew he shut down his laptop 30 minutes ago...
it seems the desktop contacts wont refresh their status