Tested and reproduced in 6.1, branch, and trunk (revision 115990). Steps to reproduce:

1. Upload 3 images to the document library
2. Set 1 image as the main asset, with the other 2 as related assets
3. Tag the main asset and 1 of the related assets as "test1". Tag the second related asset "test2".
4. Create Asset Publisher portlet and Related Assets portlet.
5. Configure tags in Related Assets portlet to only display the asset with the tag "test2".

Expected Result: Portlet will display the asset with the tag "test2" only.
Actual Result: Upon hitting save in the configuration, both related assets fail to show. Once the screen is refreshed, both related assets show and there are no saved changes shown in the configuration window.

The client would like to be able to use the filters in the Configurations to filter the assets shown in the portlet by using Tags. I received confirmation that Related Asset portlet implementation should be closer to that of the Asset Publisher portlet. It should have "add" and/or "select" buttons and it should create a bubble around the entered tags, allowing the user to filter by Tags.