HttpModule System.IO.Stream FileIOPermissions

[Philip]

I have a httpModule component which is performing GZIP and Deflate
compression of Http flows using the System.IO.Stream,
System.IO.Compression.GZipStream and System.IO.Compression.DeflateStream as
base classes. In a Sharepoint minimal trust environment I am seeing
FileIOPermissions exceptions being trapped by Sharepoint in the system event
log.... however from a functional standpoint the httpModule component is
working fine.

Since the System.IO base classes are being used for in-memory streams only
.....what would explain the FileIOPermissions exception.....and what can I do
to eliminate the FileIOPermissions exception ....provided of course that I
need to continue using the Stream classes.
Thanks