Upgrading CMM Micro using CNUT

I am having problems upgrading any of my CMM Micros using CNUT or TFTP. CNUT will show the file transfer in progress for upto 6 hours but it never completes the upgrade. I have also followed the user guide procedures on using our Tftp server but it times out and disconnects. After using either of these methods the web interface to the CMM locks up and I have to telnet to the CMM to reset it. I have used CNUT ever since it was released and before that I always used the ftp/telnet procedures for upgrades. Anybody else having this problem or any sugestions on what to do?