Ok, I think I figured it out:
1. Uninstalled Adobe Acrobate 11.0.09.
2. Turned computer off & then back on.
3. Reinstalled Adobe Acrobat 11.0.0.
4. Set to Twain.
5. Tried a scan which worked like before upgrade to Yosemite.
6. Tried to update to Adobe Acrobat 11.0.09. DID NOT WORK, JUST LIKE BEFORE.
7. Uninstalled and reinstalled Adobe Acrobat 11.0.0. WORKS GREAT
Hope this helps.