Problem with Adobe Acrobat 7.0 Connection to Internet error message

I am trying to use adobe reader 7.0, but everytime I try to open a PDF (I am reading ebooks), I get and error message 'must be connected to internet', as if acrobat thinks I am not connected to the internet, when I am.

The ebooks require authentication online, but for some reason acrobat can't see that I am online. Any one else come across this or have any ideas?

Thanks, Jason