Can't install ESXI 5.1 and 5.5 on DL585 G7

[nu938]

Greetings!

We use iPXE to install various OS' on a number HP ProLiant server models. We are using iPXE from one of the latest releases: I built it out of commit 6847232e70f7 , and have a problem installing ESXi 5.1 and newer on the HP DL585 G7 model only.
The same ipxe binaries with the same ipxe script, mboot config and the kickstart file work fine on DL580 G7, but fail on DL585 G7.

The main difference between these 2 models are their processors:
DL585 G7 has AMD OpteronTM 6376 (2.3GHz/16-core/16MB/115W) Processor (doesn't work), and DL580G7 has Intel® Xeon® E7-4870 (2.40GHz/10-core/30MB/130W) Processor (works fine)

Here is the error message (can't attach a screenshot for some reason):
"Configuration error while parsing http://xxx.xxx.xxx.3:8000/de/boot/mboot/...32-484844e
Fatal error: 15 (Not found)"

The config file that it shows as not found actually exists, and I can open it in my browser. Also, the same exact setup works on DL580 G7.
Here is our ipxe script:
------
#!ipxe

# UUID: 35393532-3431-435a-3331-343933345450
# Command: deploy
# Task ID: 1742
# OS Family: ESX
set os_media_host xxx.xxx.105.21

set web_svc_address xxx.xxx.105.21


set install_uri http://${os_media_host}/installers/ESXI55//SP2/X64
set ks_uri http://${web_svc_address}:8000/de/kickstart/35393532-3431-435a-3331-343933345450
set pe_uri http://${web_svc_address}/installers/PE
set mboot_cfg http://${web_svc_address}:8000/de/boot/mboot/uuid/35393532-3431-435a-3331-34393334545


dhcp net0
imgfree
kernel -n mboot.c32 ${install_uri}/mboot.c32
imgargs mboot.c32 -c ${mboot_cfg}
boot mboot.c32
--------


Here is mboot_cfg file:
-----
bootstate=0
title=Loading ESXi installer
prefix=http://xxx.xxx.105.21/installers/ESXI55/SP2/X64/
kernel=tboot.b00
kernelopt=ks=http://xxx.xxx.105.21:8000/de/kickstart/35393532-3431-435a-3331-343933345450 BOOTIF=78:e3:b5:0c:67:ec
modules=b.b00 --- jumpstrt.gz --- useropts.gz --- k.b00 --- chardevs.b00 --- a.b00 --- user.b00 --- sb.v00 --- s.v00 --- misc_cni.v00 --- net_bnx2.v00 --- net_bnx2.v01 --- net_cnic.v00 --- net_tg3.v00 --- scsi_bnx.v00 --- scsi_bnx.v01 --- elxnet.v00 --- ima_be2i.v00 --- lpfc.v00 --- scsi_be2.v00 --- char_hpc.v00 --- char_hpi.v00 --- hp_ams.v00 --- hp_build.v00 --- hp_conre.v00 --- hp_esxi_.v00 --- hp_smx_p.v00 --- hpbootcf.v00 --- hpnmi.v00 --- hponcfg.v00 --- hpssacli.v00 --- hptestev.v00 --- scsi_hpd.v00 --- scsi_hps.v00 --- scsi_hpv.v00 --- net_igb.v00 --- net_ixgb.v00 --- scsi_mpt.v00 --- net_mlx4.v00 --- net_mlx4.v01 --- net_mst.v00 --- ima_qla4.v00 --- net_nx_n.v00 --- net_qlcn.v00 --- qlnative.v00 --- scsi_bfa.v00 --- scsi_qla.v00 --- ata_pata.v00 --- ata_pata.v01 --- ata_pata.v02 --- ata_pata.v03 --- ata_pata.v04 --- ata_pata.v05 --- ata_pata.v06 --- ata_pata.v07 --- block_cc.v00 --- ehci_ehc.v00 --- weaselin.t00 --- esx_dvfi.v00 --- xlibs.v00 --- ipmi_ipm.v00 --- ipmi_ipm.v01 --- ipmi_ipm.v02 --- lsi_mr3.v00 --- lsi_msgp.v00 --- misc_dri.v00 --- mtip32xx.v00 --- net_be2n.v00 --- net_e100.v00 --- net_e100.v01 --- net_enic.v00 --- net_forc.v00 --- net_vmxn.v00 --- ohci_usb.v00 --- rste.v00 --- sata_ahc.v00 --- sata_ata.v00 --- sata_sat.v00 --- sata_sat.v01 --- sata_sat.v02 --- sata_sat.v03 --- sata_sat.v04 --- scsi_aac.v00 --- scsi_adp.v00 --- scsi_aic.v00 --- scsi_fni.v00 --- scsi_ips.v00 --- scsi_lpf.v00 --- scsi_meg.v00 --- scsi_meg.v01 --- scsi_meg.v02 --- scsi_mpt.v01 --- scsi_mpt.v02 --- scsi_qla.v01 --- uhci_usb.v00 --- xhci_xhc.v00 --- tools.t00 --- xorg.v00 --- imgdb.tgz --- imgpayld.tgz
build=
updated=0
-------

Any help will be greatly appreciated.
Thank you!