Well, I didn't have any old versions in reserve hiding in my download folder but I was able to find a full 9.4 install. Removed 10 and reloaded 9.4 and the scanner is working fine now.
For what it is worth, when I looked at the files I had attempted to scan after the 9.4 install I could see them and they scanned fine. For unknown reasons the files would not open with v10. Being under time to get a document scanned I didn't try everything instead I jumped back in time to get the job done. Now I have to wonder if the files were good to go and v10 just wouldn't auto launch them. If I get extra time I may try updating again and attempt to scan, then check the scanner folder to see if the files open manually.
For unknown reasons the files would not open with v10.
Try disabling the protection mode.
1. Launch Adobe Reader X and go to Edit > Preferences.
2. Select "Security (Enhanced)" from the list of categories.
3. Uncheck the checkbox for "Enable Enhanced Security" and click Ok.
4. Try repeating your workflow to verify if this fixes the problem.