Hoping to spare someone else the agony of running in circles. Discovered that I had auto discovery turned off after weeks of chasing down potential infrastructure issues. Here's the symptoms and fix (all Windows based servers, so paths may not be correct for other OSes).
Symptom: Server boots, gets an IP from DHCP but gets no PXE response and errors out with an "Error E53: no boot image found" message.
Troubleshooting steps taken: Checked the pxe.log file found in C:\Program Files (x86)\BMC Software\BladeLogic\PXE\br and located several error messages by searching for the MAC address. Several lines were found with this text (several different MAC addresses had these error messages):
[INFO] [::]  Device 00-17-a4-45-09-50: not present in db
[WARN] [::]  RPacketProcessor: Ignoring boot request from: 00-17-a4-45-09-50. MAC not registered with Provsioning Manager or has multiple entries
Fix: Edit the pxe.conf file in C:\Program Files (x86)\BMC Software\BladeLogic\PXE\br. Toward the end of the file there is a setting for auto discovery, it should look like this:
# To disable auto discovery, set to 1
# In this case the pxe server will only repsond to devices already
# present in the provisioning system i.e manually imported
Any value other than 0 will disable auto discovery and not import new server MAC addresses into BSA.
I will now go back to reacquainting my head with my desk.
Thank you for sharing this!