Dan, I remember now that I had trouble with CS5 after I first downloaded it. I called Adobe and they handled the issue promptly. I had to grant them permission to see my screen remotely which helped a lot. They removed somethings from the original download and I had to download a new version.
Anyway the process took awhile, but thy answered my call quickly and the problems were solved.
I did need the serial number as I recall, so have that ready.
You issue must be software.