You may receive the following error message when you try to import an image from your scanner into your graphics application:

"This application has failed to start because rmslantc.dll was not found. Re-installing the application may fix this problem."

or

"Unable to open TWAIN source."

This problem occurs when the system path environment variable exceeds the maximum character length expected by the CanoScan driver.

The system path is a list of folders, separated by semicolons, that identifies which folders the system should search when looking for executable files.  Although 2048 characters are permitted, the CanoScan driver fails when the system path is between 700 and 800 characters.

Many applications append their installation folders to the system path, and it is not uncommon to see system paths exceeding 1000 characters in length.

A quick workaround is to prefix the CanoScan TWAIN folder to the system path.  If this does not resolve the problem, it may be necessary to determine experimentally which path components can be safely removed.

For application developers, the system path length can be significantly reduced by removing all references to command line compilers, libraries and utilities.  A task-specific command prompt shortcut can be added to the Start Menu, extending the system path as required using a batch file to modify the command prompt environment.

Links

CanoScan 9550F Color Image Scanner
Microsoft Knowledge Base Article KB832978

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