Calendar view no longer working

Calendar view no longer working

I have a view set up to default to a calendar view. When I initially go to it, all of the data is there. However, if I switch months, the calendar goes blank, and when I go back to the month I just viewed, the data is now gone out of that one. Switching to any other month still shows nothing. If I set a filter though, the data shows. This problem just started occuring. Any thoughts/suggestions?
brenthilg