getSubCalendar Unable to determine time zone

2011-12-19 00:22:33,474 ERROR [http-9080-5] [extra.calendar3.calendarstore.ExternalCalendarDataStore] getSubCalendar Unable to determine sub-calendar 887f1297-6c2c-431a-9fe3-f186ac52de18's time zone
 -- referer: https://extranet.atlassian.com/login.action?os_destination=%2Fhomepage.action | url: /dashboard.action | userName: igrunert
com.atlassian.confluence.extra.calendar3.exception.CalendarException
        at com.atlassian.confluence.extra.calendar3.calendarstore.ExternalCalendarDataStore._getSubCalendarContentInternal(ExternalCalendarDataStore.java:121)
        at com.atlassian.confluence.extra.calendar3.calendarstore.ExternalCalendarDataStore.getSubCalendarTimeZoneId(ExternalCalendarDataStore.java:78)
        at com.atlassian.confluence.extra.calendar3.calendarstore.ExternalCalendarDataStore.getSubCalendar(ExternalCalendarDataStore.java:165)
        at com.atlassian.confluence.extra.calendar3.calendarstore.CalendarDataStoreCachingDecorator.getSubCalendar(CalendarDataStoreCachingDecorator.java:117)
        at com.atlassian.confluence.extra.calendar3.calendarstore.DelegatingCalendarDataStore.getSubCalendar(DelegatingCalendarDataStore.java:103)
        at com.atlassian.confluence.extra.calendar3.calendarstore.InternalSubscriptionCalendarDataStore.getSourceSubCalendar(InternalSubscriptionCalendarDataStore.java:157)
        at com.atlassian.confluence.extra.calendar3.calendarstore.InternalSubscriptionCalendarDataStore.fromStorageFormat(InternalSubscriptionCalendarDataStore.java:107)
        at com.atlassian.confluence.extra.calendar3.calendarstore.InternalSubscriptionCalendarDataStore.fromStorageFormat(InternalSubscriptionCalendarDataStore.java:46)
        at com.atlassian.confluence.extra.calendar3.calendarstore.AbstractCalendarDataStore.getSubCalendar(AbstractCalendarDataStore.java:189)
        at com.atlassian.confluence.extra.calendar3.calendarstore.DelegatingCalendarDataStore.getSubCalendar(DelegatingCalendarDataStore.java:103)
        at com.atlassian.confluence.extra.calendar3.DefaultCalendarManager.getSubCalendar(DefaultCalendarManager.java:174)
        at com.atlassian.confluence.extra.calendar3.CalendarWebPanel$2.apply(CalendarWebPanel.java:168)
        at com.atlassian.confluence.extra.calendar3.CalendarWebPanel$2.apply(CalendarWebPanel.java:164)
        at com.google.common.collect.Iterators$8.next(Iterators.java:782)
        at com.google.common.collect.Iterators$7.computeNext(Iterators.java:644)
        at com.google.common.collect.AbstractIterator.tryToComputeNext(AbstractIterator.java:141)
        at com.google.common.collect.AbstractIterator.hasNext(AbstractIterator.java:136)
        at com.google.common.collect.Iterators.size(Iterators.java:147)
        at com.google.common.collect.Collections2$FilteredCollection.size(Collections2.java:222)
        at com.atlassian.confluence.extra.calendar3.CalendarWebPanel.retrieveEventsAsync(CalendarWebPanel.java:366)
        at com.atlassian.confluence.extra.calendar3.CalendarWebPanel.getEventsForDashboard(CalendarWebPanel.java:187)
        at com.atlassian.confluence.extra.calendar3.CalendarWebPanel.renderDashboardCalendar(CalendarWebPanel.java:141)
        at com.atlassian.confluence.extra.calendar3.CalendarWebPanel.getHtml(CalendarWebPanel.java:93)
        at com.atlassian.plugin.web.descriptors.DefaultWebPanelModuleDescriptor$ContextAwareWebPanel.getHtml(DefaultWebPanelModuleDescriptor.java:141)
        at com.atlassian.confluence.plugin.descriptor.web.ConfluenceWebInterfaceManager$ExceptionHandlingWebPanel.getHtml(ConfluenceWebInterfaceManager.java:174)
        at sun.reflect.GeneratedMethodAccessor543.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.doInvoke(UberspectImpl.java:389)