Request.BinaryRead ASp error

Why does the error below occur whenever the statement
Request.BinaryRead(Request.TotalBytes) is executed for uploads larger than
100K?  I thought the 100K limit applied only to Request.Form.  This does not
occur with smaller uploads.  This is running on an IIS 6 server with full
FP2002 extensions.

ERROR:
Request object error 'ASP 0104 : 80004005'
Operation not Allowed