Problem with display states

Using SW 2010 64 bit.

Have an assembly with a strange problem. There is a display state that does not have a name and the name cannot be change/ edited. The display state cannot be activated or deleted. If I try and delete the display state all other display states take on the sate of the display state that was active at the time I tried to delete it.

Have tried going into PW and detaching all the material color attachments as I read somewhere that that may be a problem but no luck.

Any advice/suggestions appreciated

SolidworksAssemblies