Upgrade from 4 to 5 stalls

When "Running package scripts" during installation of Parallels 5 on my Macbook Pro (Snow Leopard), the installation process stalls near the end with "About a minute" remaining, crawls for an hour or so, and finally hangs just short of completion. Happens every time I try to install the downloaded installer package.

For no particular reason I tried to upgrade 4.0.3844 to build 3846, and that doesn't work either. I aborts immediately after I click to "run a program to determine if the software can be installed."

Any insight as to what may be underlying these reactio

 

Aha! The problem was solved by downloading Parallels 5 again from the Nova website. This time the installation succeeded. I have since purchased another copy for my wife's IMac, and that download installed with success, too.