[syslinux] PXELinux and Boot Disk Failure on Dell Optiplex 740

[Massey, Sean]

I just started having an issue with PXELinux with one particular model
of computer.  The issue appears to occur on Dell Optiplex 740 computers,
and any disk image that we try to boot with PXE Linux comes up with a
Boot Disk Failure for two images or Cannot Load Kernel error for Dell
Diagnostics.  The error only appears to occurs on the Optiplex 740
model.  I've tested PXE Linux and our boot disk images with Dell
Latitude E6400 and Dell Optiplex GX620s, and they were able to boot the
images successfully.

This issue started today - as of Friday, we did not experience this
issue with the Optiplex 740.

Our version of PXELinux and Memdisk is 3.72.  Our TFTP server is TFTPD
3.28.  The Optiplex 740 has a Broadcom UNDI PXE-2.1 V. 9.0.10, and we've
tested this against multiple 740 BIOS revisions to the same effect.  Two
of the boot files are old 3Com Boot Services disk images for Symantec
Ghost and the third is a Dell Diagnostics .img file.

This issue just started occurring today.  As of last week Friday, we
were able to boot the 740s over PXE.  On Friday, I had changed the order
of some items in the pxelinux.cfg\default file, but the issue didn't go
away when I restored the old menu from backup.  I also restored the boot
image files from a known good backup, updated our PXELinux and Memdisk
files to 3.73, and TFTPD32 to version 3.29.  We also went back to our
old 3Com Boot Services PXE deployment, and the Optiplex 740s were able
to boot the two images for Ghost.

Is there anything that I'm missing here?  Is there anything else I need
to try?

Thank you,

Sean Massey
Desktop Administrator
Faith Technologies