View filters behave a bit different in 2008 and 2009. We have a filter called "Filtered Objects" in our template that applies to all categories and which is Filtered By based on the following Filter Rule in RAC 2008. (ScheduleSorter Project parameter equals <nul> or any other value)
When opened in RAC 2009, the filter changes to:
This can cause quite a confusion, especially if the filter is used to turn on/off the visibility of the objects... based on the unwanted behavior, it can switch off all the objects in view when opened in 2009!!!
I will report this to Autodesk.