Is that a BO report in V12.0?
I looked in my v12.0 and could not locate"Resource availability". Neither could I locate a portlet with that name.
It is not listed in Crystal Reports Stock Report Descriptions nor in Actuate Stock Report Descriptions.
The behaviour you describe fits a portlet using the system slices, but there should be an error "The timeperiods don't exist"
See eg.
Resource Planning>Allocations>Weekly Details - Time Scale Values - ISSUES
97477438
Martti K.