I've got an assembly that is behaving strangely.

Components no longer move by dragging if they have ANY mates.

Components will drag freely if NO mates applied.

NO the component is not fixed.

NO the component is not part of a sub-assembly

System option "Move components by dragging" IS checked.

It is ONLY this assembly.  Other assemblies work fine.

Anybody else experienced this or have any ideas or a solution?