It sounds like you've found a bug in Google Calendar itself. Is your
primary calendar hidden? If so, you might be affected by a known issue
described here:
http://www.google.com/support/calendar/bin/answer.py?answer=55677
"Currently, some users whose primary calendars are hidden from view
are unable to create new calendars. If you're receiving an "Oops, we
couldn't load details for your calendar, please try again in a few
minutes" error when creating a new calendar, please follow the steps
at How do I "unhide" a calendar? to unhide your primary calendar.
After you've verified that your primary calendar is displayed, please
log out and log back in to Google Calendar before creating a new
calendar."
If not, this may be something Google is unaware of. You can report
problems with Google Calendar here:
http://www.google.com/support/calendar/bin/request.py?contact=1
Please let us know what you find out.
Thanks,
Charlie