I have been setting up a PXE boot server and have had issues with TFTP.
From experiment it seems the TFTP server in SME 7.5.1cannot cope with a symbolic link to an ibay.
Until I moved the files from the ibay to /tftpboot I kept getting file not found when network booting.
I have posted this here in the hope of shortening the time it takes anyone else to resolve similar issues.
Cheers
Kevin