Chuck, I can certainly understand your frustration as I certainly would be in your shoes.
To better mitigate this, there should not be a link to installation instructions then on the Members Area where the member downloads the software. This is confusing to the customer as the customer may not read all that you point out, but they certainly will go to the Members Area to download their software...and for the one place they are certain to go....they get the incorrect/out dated instructions. One, like me, would assume the link to the instructions is what we are to follow.
So, if the link doesn't get updated as often as the instructions in the downloaded archive...then why even have this link? Only reason I can see keeping this link available is to keep you pulling the last few stubbles of hair trying to grow on top of that head of yours.
