As you have read in other threads, Acrobat X on Windows has a serious scanning problem with HP and possibly other scanners.
Whereas in Acrobat 9 scanning worked reasonably well, Acrobat X seems to be unable to cope with scanning documents from the flat bed of a multifunction scanner.
So, if you are scanning from the feeder, scanning works, but if you are scanning from the flatbed, you will get a brief pause and the phrase SCANNING CANCELLED.
This is, of course, not acceptable.
The problem is that Acrobat X does not play nicely with the scanner drivers. Previously, Acrobat 9 would "auto-detect" the source of a document, using the feeder if loaded, and "falling back" to the flatbed otherwise. However, Acrobat X does not fall back. If there is nothing loaded in the document feeder, the scan will be cancelled by Acrobat X.
The workaround - and I would NOT call this a "solution" - is to use only the "Custom Scan" command from Acrobat X. When the window pops up, choose the "Options" button and select "Native Mode" and "Show Scanner's Native Interface" from the two menus. (Acrobat X does seem to remember these settings at least within a session, so if you're scanning multiple documents you only need to do this once.) Then scan.
You will see a new window pop up - the scanner's "native interface." On my computer, this window shows up BEHIND the Acrobat X screen (annoyingly) so you have to watch for it and click forward. Be sure to select "flat bed" from the "document source" menu. On my computer, this setting is NOT remembered between scans, so you have to do this for EVERY SCAN. Then, the document will scan, and you can do what you want with it in Acrobat X.
Needless to say, this is a long, painful, slow process, especially if you're scanning lots of flatbed items, as I do. Hence it's a "workaround" and NOT a "solution".
Thank you!