I developed and deployed an ASP.net website. One of my clients, trying
to access the website are getting and "Object Reference Not Set to an
Instance" error.  They are behind a firewall.

The website opens fine in all other machines.

I looked up on the internet and saw a couple of message posts
mentioning commands like URLReferrer can make the firewall blow the
page by not executing those commands.

But in my case, I dont have that command being used anywhere in my
project and I dont know what type of commands cause the firewall to
act the way it does. Is there a certain pattern or how does it
work...any information helps!!

I cant debug either since it blows up on only those client machines
and works fine on the development machines.