Shelley -
It's important that the recommendation it gives is followed.
The december version is more strict on security. Judging by the message, you have a customized screen that has a design flaw. It may have existed for some time, but now it is being flagged. As the message suggests, the recommendation is to check out the filters of the grid and make sure they make sense. Most likely, make sure the grid is not filtering on fields that no longer exist on the screen. In the December version, if there are any grid filters that don't completely make sense, the grids will show nothing, rather than ignore them. While this is inconvenient to fix, it ultimately is doing what you should want it to do - validate your design and make sure it is logical, to avoid the risk of displaying data to your users that you don't want to show.
The reason we had the November version available was to let you use the screen the old way temporarily, until you had a chance to follow the displayed recommenation.
Paul