Poof! A new Configuration

I ahev a sheet metal part. It is mirrored to create a configuration of the part. Whenever I make a change,

the change shows up in the other configuration as suppressed. These "new" configurations build up as

long as I make changes. I can delete these bogus configs. But the process willl continue.

What is this and how do I stop this madness?

I am using SW 2011 64 bit

Thanks.

SolidworksAssemblies