I am assuming you are attempting to open them up via a local install of both Unisphere Server and Client (what used to be known as off-array).  You need to make sure that your local install is same or better than the version of Unisphere running on the array that generated the NAR files.  Regardless, I would just always try to run the latest which as of this post is:  Unisphere Server: v1.2.2.1.0045 Unisphere Client: v1.2.2.1.0036  From my experience, this usually/always accounts for the error.
Hi,  Everytime I try to download a NAR file attached in an SR or as an attachment file in a discussion on ECN, and try to open up, it throws an error saying incorrect/unsupported version. I tried converting it using unix2dos/dos2unix just in case, but still didn't work. Does anyone have any solution to this problem?
Issue with NAR files