How do I open emails with nothing in the subject line

Every once in a while I get emails from people with nothing in the subject line.  Something is blocking my email from opening them.  Is this a function of the Norton internet security v. 2011?  If so, is there some sort of over ride and how do I use it?

 

I am not thrilled with shutting off my internet security in order to read the email since I have no idea if the incoming email is infected or if the writer merely forgot to write something there.

 

I have win xp ser pack 2 and SBC Global internet (provided by ATT)

 

Thanks,

G