Unable to Install to Multiple Computers

I have a license for 3 computers but when I attempt to install, I receive an error from your website saying "You are attempting to install a non-windows product.  Please select a Windows compatible product to install."  All my machines are running Win7 and it is a Windows Product.  This occurs from your management page when I attempt to install NIS (following the E-mail link).  I had no issues with the first install.  But on the second and third machines, this is the problem.