Binary Grid scaling

[Renaud]

One of the layers of our map is a raster image (see gdalinfo output) 
which represents a piece of land, surrounded by a NODATA area. The 
display through mapserver is correct as long as the displayed area 
doesn't include any NODATA dots. Sadly, if a part of the displayed box 
has a NODATA area, the latter appears black while the land is white.

Driver: AIG/Arc/Info Binary Grid
Size is 5072, 2944
Coordinate System is `'
Origin = (41800.000000,168200.000000)
Pixel Size = (50.00000000,-50.00000000)
Corner Coordinates:
Upper Left  (   41800.000,  168200.000)
Lower Left  (   41800.000,   21000.000)
Upper Right (  295400.000,  168200.000)
Lower Right (  295400.000,   21000.000)
Center      (  168600.000,   94600.000)
Band 1 Block=317x4 Type=Float32, ColorInterp=Undefined
   Min=0.024 Max=0.264
   NoData Value=-3.40282e+38


It seems to be a scaling problem... We have played around with
  *the PROCESSING "SCALE=AUTO" or "NODATA=..." options,
  *classes etc.
from within the mapfile, and tried to convert the image to another 
format with gdal_translate, but nothing worked.

Thank you for your help,
Renaud Detry.