Problems with MacOS 8.6 client since upgrade from 10.4.8 to 10.4.9

Hello all, Since we went from MacOS X Server 10.4.8 to 10.4.9 I am seeing very strange behaviour from an older layout/Quark XPress machine still running MacOS 8.6. After doing the upgrade the file server will now disconnect the 8.6 client accessing it via TCP/IP and AFP. This will only happen with files ecceding approximately 800k [b]*and*[/b] with operations creating new files like "save as..." oder copying from the local 8.6 desktop to the remote 10.4.9 volume. Any ideas would be greatly appreciated! Thanks, Pascal