Diane,

It is more likely that someone has compromised your isp and is using
it to spam thereby getting your isp number black listed. They might
not even be spamming the site you want to visit..Make sure you have a
good fire wall and security system.  As far fetched as it may seem,
there are MANY people out there that are trying to get into your
computer to steal information like  your isp number so they can
continue their nefarious activities.  Such a sad time in which we
live.

~Jill