Are you sure you have the file name correct?  A google web search
fails to locate a single reference to any file named MASRAST.DLL

There is, however, a file named MAXRAST.DLL that is part of the
Visioneer Paper Port software and I suspect that is what you are
referring to.

1.  Check with the Visioneer web site for any updated software or
drivers for your Paper Port software and/or Visioneer Scanner.

2.  If the error message is on a "Blue Screen Of Death" then please
provide the complete verbatim text of the error message from that
screen.   If it is a pop-up error message window then the next time it
happens press Alt+D while the error message is still on the screen to
bring up the Detailed Error Message.   Copy the first portion of the
detailed message, up to the word Registers:, and post that information
back here.   That will give us something more specific to work with.

Good luck

Ron Martell     Duncan B.C.    Canada