You wouldn't be able to apply the new UV's to the Poser Bear OBJ, you would get "incompatible facet structure".

Have to assume OP is using proper OBJ file.  I have the freebie in question but it works fine for me.

The only thing I can think is maybe the blBear.rsr file was not deleted and is interfering.  But I'm not sure if modern versions of Poser even look at that anymore.