When I first tried installing SL from a CD, I ran into the "must download update." After downloading the update, I got a message box saying:
"NSIS Error - Installer verification falied. This could be the result of an incomplete download, a failing disk, or (possibly) corruption from a virus. You can try to force an install using the /NCRC command line switch (but it is NOT recommended)."
Downloading the install from the web worked fine and I was able to play SL. Now, with the 1.2 update, I've run into the same problem. The "must download update" gave me that same error. So I uninstalled SL and downloaded the 1.2 installer. Guess what, I get the SAME error when I try to run the installer!!!! I did a virus scan (clean) & my hard drive isn't full. Any suggestions???