Does anyone know why an assembly will suddenly change to under defined?  I'll have it where have an assembly fully defined, and when I add a new part, some of the parts that where already there will change to under defined.  Then if you suppress or delete the new parts, the rest go back to being fully defined.  I sometimes have the same issue when Solidworks updates.  I have assemblies that where fully defined, and after I updated solidworks I'll have assemblies that most of the parts are now listed as being under defined.  It makes it hard to know if the assembly is ever done.