Virus scanner unavailable. The attachment may or may not contain a virus.

I get this message when I go to send a particular .zip file or open the same .zip file I created. It only happens with this one .zip file sent through yahoo email. (I believe it is the Norton Antivirus sent through yahoo that cannot scan this file.

 

I checked the file with another online scanner and it said it was okay. Does anyone know what is happening?