Could not access any events for the [Orange] group.

Creating Group events works well - when on a particular group home page Group Events Block only shows current groups events - fine so far. BUT at the bottom of each event node next to [Add new comment] and [Calendar] a new link has appeared [(group name) Calendar], which links to /og_calendar/6 for example. But clicking on this link always produces
"Group Calendar
Could not access any events for the [Orange] group. "
even though I created all the groups and am user 1.
I went back to a clean drupal5.2 install and still it gives the same result.
I have put a temporary demo site at
http://74.220.203.213/ogcaltest/
with the user1 name AND password of
demo

please advise - thanks