Clients do not properly boot to a PXE Menu whether through a Reboot to Automation task or by manually booting client.
After the nic boot agent splashes its messages, the process ends with PXE-M0F.
NBS General settings were not configured to respond to computer under either of the scenarios(unknown, predefined, or managed).
Configuring NBS settings for SBS to respond to clients with a specific preboot configuration allowed clients to boot with the PXE boot menu as expected.
See "Chapter 4 Setting up preboot environment" in the Symantec™ Deployment Solution 7.5 powered by Altiris™ User Guide
Further note: PXE M0F is not an error and reflects a successful PXE boot encounter as far as the nic's boot agent is concerned.
Newly installed or upgraded Deployment Solution 7.5