I purchased a UCS-E140DP-M1 blade off eBay for $900 so we could throw it in one of our ISR G2s and play with it.  It powered on fine, and the first step was to get the firmware upgraded.  The CIMC went from 1.0 to 2.4.1 no problem, but upon taking it to 3.1.3, the blade would not boot.  Seemed to be stuck at the BIOS prompt..

My theory right away was an incompatibility between the CIMC and the BIOS.  The original BIOS version shipped was 4.6.4.8, but the newer versions were lower, indicating something major had changed.  I attempted multiple times to to upgrade the BIOS to the versions matching CIMC 1.0.2, 2.4.1, and 2.5.0.3, but would always get some error message.  Common output looked like this:

Router#ucse subslot 2/0 session imc 
Trying 10.10.10.10, 2131 ... Open
Username: admin
Password: 
E140DP-FOC16490HEF# scope bios
E140DP-FOC16490HEF /bios # show detail
BIOS:
    BIOS Version: 4.6.4.8
    Boot Order: CDROM:Virtual-CD
    FW Update/Recovery Status: Error, Update invalid
    Active BIOS: backup

After downgrading the CIMC back to 2.4.1, I was copy and map huu-2.4.1.iso, follow the wizards, and then upgrade the BIOS.  This looked much better.

E140DP-FOC16490HEF /bios # show detail
BIOS:
    BIOS Version: "UCSED.1.5.0.2 (Build Date: 05/15/2013)"
    Boot Order: CDROM:Virtual-CD
    FW Update/Recovery Status: Done, OK
    Active BIOS on next reboot: main

So long story short – use the HUU to do all firmware updates, so the CIMC and BIOS firmware versions are in sync.