Where do you have this filter applied? At the form attribute level or the object attribute level? It probably wouldn't hurt to remove it from where you currently have it.. save and then add it back. It might be confused by just changing the query but if it sees you as "applying a new one", it may act differently.
If you have screenshots you could provide that could be useful as well. Could you supply the version too if the above doesn't work?
The filter is applied at object attribute level. I have removed the filter, saved and readded the filter. However no change. We are using version 7.5 SP1.