block editing acad2010

I just started using acad2010. I have come across something that is a pretty big problem for the work I do.

if I have a block, say a floor plan with a block called "hss" on it, and I want to add another HSS block to it usting RefEdit, I get this message:

"Block hss was not added to the work set.

Its name conflicts with a block already in the work set."

It worked fine in 2007. I could add anything I wanted.

example file attached.

block.dwg

Download and install the Autocad 2010 Update 1.

that worked!