problem with design table

We are using design tables for screws, washers, nuts etc., they were created in 2007. We upgraded to 2008 and are now experiencing this problem;

added new length to screw design table and it updated just fine, go to assemblies were a specific screw from a family is called out and they all updated to the new screw ( the last configuration saved) even though that was not the desired outcome, only wanted to add a new screw config. and place it in a new location.

Thanks in advance for the help.