OK, here is more information, as per the tech person from the scanner company.
The C decleration from the .h file:

  BUICScan - Scan one check and place the image
      in the files named by the passed parameters.
      iJobType specifies which images (information)
      is captured and stored.

  PARAMETERS:
      iJobType    -
                     1 - Front
                     2 - Back
                     3 - Front and Back
                     4 - MICR
                     5 - Front and MICR
                     6 - Back and MICR
                     7 - Front, Back and Micr
      lpFront     -  File name for front of the check image.
      lpLenFront  -  Length of the file (ASCII) for the front of the check image.
      lpBack      -  File name for back of the check image.
      lpLenBack   -  Length of the file (ASCII) for the back of the check image.
      lpCode      -  File name for MICR of the check.
      lpLenCode   -  Length of the file (ASCII) containing the MICR.

debug information from the scanner:

BuicInit called
      C:\WINNT\BUICScan.INI found and SCSI parameters are read (Up to 8
Scsi cards with the default location for the scanner at Adapter 2,
Target ID 2
 
      Items under [DOUBLE LIGHT SOURCE] in buicscan.ini (Defaults)
941859582 -- BUICSetParam(51,0)     Manual Feed Off
941859582 -- BUICSetParam(61,0)     Redo Drop Out OFF
941859582 -- BUICSetParam(62,1)     Format 1
941859582 -- BUICSetParam(63,50)    Front Intensity 50
941859592 -- BUICSetParam(64,60)    
941859592 -- BUICSetParam(65,10)    
941859592 -- BUICSetParam(66,0)     
941859592 -- BUICSetParam(67,1)     
941859592 -- BUICSetParam(68,50)    
941859592 -- BUICSetParam(69,60)    
941859592 -- BUICSetParam(70,8)     
 
 
 
941859602 -- BUICSetParam(55,0)     DSP OFF
941859602 -- BUICSetParam(47,0)     External Reader Off
941859602 -- BUICSetParam(1,0)      MICR Enable OFF --- MICR: Enable=0
941859602 -- BUICSetParam(3,0)      Badge Read off
941859602 -- BUICSetParam(4,0)      Endorser off
941859602 -- BUICSetParam(31,0)     Printer off
941859602 -- BUICSetParam(32,0)     Sorter off
941859602 -- BUICSetParam(7,1)      Double Feed On
941859602 -- BUICSetParam(1,1)      MICR Enable ON --- MICR: Enable=1
941859602 -- BUICSetParam(2,1)      MICR Font E13B
941859602 -- BUICSetParam(107,2)    MICR Keep Spaces
941859602 -- BUICSetParam(14,0)     Initial MICR Position
941859612 -- BUICSetParam(71,1000)  MICR End Postion 1000
      Aux Reader
941859612 -- BUICSetParam(72,1)     
941859612 -- BUICSetParam(73,1)     
941859612 -- BUICSetParam(74,0)     
941859612 -- BUICSetParam(75,1000)  
941859612 -- BUICSetParam(76,3)     
941859612 -- BUICSetParam(77,0)     
941859612 -- BUICSetParam(78,1)     
941859622 -- BUICSetParam(79,0)     
941859622 -- BUICSetParam(49,1)     Sorter Input
941859622 -- BUICSetParam(39,1)     Sorter Alogithm
941859622 -- BUICSetParam(80,20)    Sort init string
941859622 -- BUICSetParam(81,244)   Sort End string
941859622 -- BUICSetParam(82,1)     Sort Eject pocket
941859632 -- BUICSetParam(84,0)     Printer Init Position
941859632 -- BUICSetParam(85,0)     Printer Selection
941859632 -- BUICSetParam(86,80)    Printer Intensity
941859632 -- BUICSetParam(140,185)  Intensity 12 
941859632 -- BUICSetParam(87,6)     XPIXELD
941859632 -- BUICSetParam(141,3)    XPixelD12
941859642 -- BUICSetParam(88,1500)  Clean44
941859642 -- BUICSetParam(89,480)   Clean18
941859642 -- BUICSetParam(90,60)    Clean 6
941859642 -- BUICSetParam(91,5)     Clean 2
941859642 -- BUICSetParam(33,0)     PrintBMP No
 
941859652 -- BUICSetParam(54,2)     Setup Format
941859652 -- BUICSetParam(42,1)     Front Only On
941859652 -- BUICSetParam(43,0)     Front/back Off
941859652 -- BUICSetParam(23,0)     BW Capture
941859652 -- BUICSetParam(45,0)     GrayLevel 4 
 
941859652 -- BUICSetParam(6,1)      200 dpi
941859662 -- BUICSetParam(11,10)    Front threshold 10 (0 to 15)
941859662 -- BUICSetParam(12,10)    Back Threshold 10
 
941859662 -- BUICSetParam(36,1)     Image Cropping On
941859662 -- BUICSetParam(37,1)     Rotate On
941859662 -- BUICSetParam(19,0)     ClipArea X1
941859662 -- BUICSetParam(21,1500)  ClipArea X2
941859672 -- BUICSetParam(20,0)     ClipArea Y0
941859672 -- BUICSetParam(22,864)   ClipArea Y1
 
      RS232 Setting
941859672 -- BUICSetParam(93,0)     
941859672 -- BUICSetParam(94,3)     
941859672 -- BUICSetParam(96,1)     
941859672 -- BUICSetParam(95,0)     
941859672 -- BUICSetParam(97,0)
      
941859672 -- BUICSetParam(104,1)    Zero Terminated Strings for
Filenames
941859672 -- BUICSetParam(115,3)    Micr Edge setting
941859682 -- BUICSetParam(134,0)    Stats Off
941859682 -- BUICSetParam(139,8000) Reconnect Delay for USB1.1
941859682 -- BUICSetParam(105,1)    Tiff MICR TAG On
941859682 -- BUICSetParam(106,1)    BMP Load Once On
 
941859682 -- BUICSetParam(98,40)    Double Feed Len
941859682 -- BUICSetParam(133,40)   Double Feed Delay
941859682 -- BUICSetParam(108,64)   Image Cropping Threshold
941859692 -- BUICSetParam(109,500)  Image Wait 500
941859692 -- BUICSetParam(110,75)   JPEG Quality
941859692 -- BUICSetParam(111,0)    Enable Scan Off
941859692 -- BUICSetParam(116,0)    MICR Verify Off - MICR OCR is
disabled 
                                    called directly.
941859692 -- BUICSetParam(117,0)    MICR Log OFF
941859692 -- BUICSetParam(142,0)    Hong Kong Rules Off
941859692 -- BUICSetParam(118,96)   Gray Threshold 96
941859692 -- BUICSetParam(143,40)   Photo Out White Threshold
941859692 -- BUICSetParam(144,15)   Photo Out White Tolerance
941859702 -- BUICSetParam(145,1)    Photo Out Enabled
      DCC Scan Settings
941859702 -- BUICSetParam(146,6885) IQA Tests
941859702 -- BUICSetParam(147,450)  Start Threshold
941859702 -- BUICSetParam(148,750)  End Threshold
941859702 -- BUICSetParam(149,150)  Inc Threshold
941859702 -- BUICSetParam(150,200)  200 dpi JPEG
941859712 -- BUICSetParam(151,1200) Max Speckles
941859712 -- BUICSetParam(152,5)    Min MICR Quality
941859712 -- BUICSetParam(153,60)   Max Bent Corner
941859712 -- BUICSetParam(154,26)   Max percent of black pixels
941859712 -- BUICSetParam(155,85)   Max Tiff Image Size
941859722 -- BUICSetParam(156,1)    DCC Scan Options
941859722 -- BUICSetParam(157,0)    Low MICR Quality Confidence Flag
941859722 -- BUICSetParam(92,4)     Image Format Tiff Hor.
      
941860593 -- funcTS400SetPrint(34,0,)
      Set PrintString at offset zero to "" string.
 
941860593 -- Leaving BUICInit 
 
941860593 -- BUICSetParam(31,0)     Printer off
 
941866352 -- BUICScan(F.TIF)  
 
941866352 -- funcTS400ScanSetup 1   
941866352 -- funcTS400ScanOne 
941866352 -- funcTS400ScanReadInit  
941866352 -- funcTS400ScanReadInit - TSOpenScan 
941868875 -- funcTS400ScanReadInit - Exiting    
941868875 -- funcTS400ScanRead      
941868875 -- 1ScanRead: iFile, iStatus = 0      
941868875 -- iImageFormat = 4, iGray256Level = 0      
941868875 -- 1ScanRead: iFile, iStatus = 0

his comment:
At this point we are trying to transfer the Images and the MICR Line.
Since the BUICAP32.dll allocates memory buffers for the images, I must
assume that the buffer provided for the MICR Line on BUICScan function
is not valid.

941895093 -- BUICExit Called