I encountered a scenario where I was unable to delete the last connection filter in SharePoint 2010. I do now know if this occurs because of a certain cumulative update but this blog helps you delete this last filter.
It is possible to set an connection filter in your User Profile Service Application to NOT sync disabled users or users that do not have an expiration on their password. In this scenario I have created a filter for disabled users.
This filter keeps returning when I click on ‘Remove’ and on ‘OK’. I can only delete this filter when I create an addition filter, but it is again not possible to successfully remove the newly created filter.
You can delete this filter using the ForeFront Identity Manager Client that is located under the following location:
C:\Program Files\Microsoft Office Servers\14.0\Synchronization Service\UIShell
Click on ‘Management Agents’ and you can view your created synchronization connections.
Open the properties for the connection where you want to delete the filter and navigate to ‘Configure Connector Filter’
Click on ‘User’
and delete the filter from this list and click on ‘OK’
Navigate back to SharePoint and the User Profile Service Application and you can see that there are no items to show in the filter view