I've spent the last 4 hours trying to "cure" this, to no avail. You are not alone. There appears to be a fatal bug with the 10.0.1 program. Hopefully there be a patch soon. This is bull!!
Oh btw, I could not uninstall the app because it hadn't fully installed. If yours did...uninstall and try to put back the old Adobe Reader 9. I restored to an earlier date and that didn't help either.
What browser are you running?
I'm having this problem but only in Firefox. I can open the pdfs in IE without a problem.
I'd love to get back to ver. 9.4 but haven't been able to do so. Forget the instructions on the website as they don't seem to work.