This is usually seen if you are using a Terminal Server and is caused because the TWAIN files in Windows folder are not available to the Windows user under Terminal Services.
Copying the TWAIN DSM (twain_32.dll) and DSM into the user’s Windows directory will fix the issue.
Instructions to do this is below...
Step1: Copy <Windows Drive>:\Windows\twain_32.dll and the entire <Windows Drive>:\Windows\TWAIN directory into C:\Documents and Settings\UserName\Windows, or equivalent directory.
Now start SOHODOX and go to the Scan window, the scanner should be listed in the list of scanners drop down. If this does not resolve the issue then go to Step 2
Step 2: Redirection by performing a registry change that prevents the application/operating system from substituting the "user’s" Windows directory for <Windows Drive>:\Windows.
Registry change example: [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Terminal Server\Compatibility\Applications\<Application Name Here>] “Flags”=dword:00000408
Important! Serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the link below...
Note: As this is scanner driver related you will have to contact your scanner vendor for further assistance.
For more information about this issue read this article...