I find that I can access the group fine with using links in the emails/post responses I see.
It seems its in the full link connected to the groups main url.
the link from search engines: http://launch.groups.yahoo.com/group/Simmons_Drums/
the one that allows me to access the group: http://groups.yahoo.com/group/Simmons_Drums/
so something to do with 'launch' in the URL