The message is quite old but I will answer here for others who has the same problem.
A possible cause may be that the "TWAIN Source Manager.Shlb" has been replaced with an older version.
To resolve this issue, please download the Mac OS X Data Source Manager (DSM) from
www.twain.org .
The exact download link is:
http://www.twain.org/mac/TWAIN_for_Mac_OS_X_SDK.dmg.bin1. Click on the Download Now option.
2. Once the file is downloaded and the disk image is mounted, double-click it to open it.
3. Open the Libraries folder and then copy the file "TWAIN Source Manager.Shlb" to the following location: Library/CFMSupport/ on your hard disk.
4. Restart your Mac.
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