GDAL/ECW Fails for high resolution views of large images

[steve.lime@…]

Frank: Running into trouble when generating high resolution views of very large 
ECW images. Using MapServer 4.5, latest ECW toolkit, CVS-based GDAL (downloaded 
on 3/10.05) on SuSE 9.0. Here's the gdalinfo from the image in question (~33Gb):

stlime@noah:/r01/data/drs/data/gen/state/mn> gdalinfo img_fsa01bim4.ecw
Driver: ECW/ERMapper Compressed Wavelets
Size is 555647, 662765
Coordinate System is:
PROJCS["UTM Zone 15, Northern Hemisphere",
    GEOGCS["NAD83",
        DATUM["North_American_Datum_1983",
            SPHEROID["GRS 1980",6378137,298.257222101,
                AUTHORITY["EPSG","7019"]],
            TOWGS84[0,0,0,0,0,0,0],
            AUTHORITY["EPSG","6269"]],
        PRIMEM["Greenwich",0,
            AUTHORITY["EPSG","8901"]],
        UNIT["degree",0.0174532925199433,
            AUTHORITY["EPSG","9108"]],
        AXIS["Lat",NORTH],
        AXIS["Long",EAST],
        AUTHORITY["EPSG","4269"]],
    PROJECTION["Transverse_Mercator"],
    PARAMETER["latitude_of_origin",0],
    PARAMETER["central_meridian",-93],
    PARAMETER["scale_factor",0.9996],
    PARAMETER["false_easting",500000],
    PARAMETER["false_northing",0],
    UNIT["Meter",1]]
Origin = (187478.000000,5471805.000000)
Pixel Size = (1.00000000,-1.00000000)
Corner Coordinates:
Upper Left  (  187478.000, 5471805.000) ( 97d18'3.25"W, 49d19'7.87"N)
Lower Left  (  187478.000, 4809040.000) ( 96d51'26.05"W, 43d22'8.97"N)
Upper Right (  743125.000, 5471805.000) ( 89d39'7.83"W, 49d21'1.56"N)
Lower Right (  743125.000, 4809040.000) ( 89d59'52.66"W, 43d23'41.41"N)
Center      (  465301.500, 5140422.500) ( 93d27'5.45"W, 46d24'59.34"N)
Band 1 Block=555647x1 Type=Byte, ColorInterp=Red
  Overviews: arbitrary
Band 2 Block=555647x1 Type=Byte, ColorInterp=Green
  Overviews: arbitrary
Band 3 Block=555647x1 Type=Byte, ColorInterp=Blue
  Overviews: arbitrary

Everything's great until zooming in when I get an error:

msDrawMap(): Image handling error. Failed to draw layer named 'fsa'. <br>
An error has occurred: Error 48 "Could not perform Read/Write o: Unable to 
access file. GDALRasterIO() failed: drawGDAL() 

I've tested a number of extents and with this image the threshold for the error 
is approximately an extent with 6000 meters on a side (output image size 
500x500).

Steve