Hopefully this helps save someone some grief out there...
We just got a brand new batch of Gen8s running ILO4 (mix of DL385p and BL465c). All came with ILO4 Firmware 1.32. When trying to load Windows 2012 R2 on the servers via Virtual Media, we kept getting the following generic "Load Driver" error message during Windows Setup:
"A media driver your computer needs is missing. This could be a DVD, USB or Hard disk driver. If you have a CD, DVD, or USB flash drive with the driver on it, please insert it now."
We tried various things to troubleshoot, including using a new ISO imsage, loading various drivers, and even loading previous version of the OS (Windows 2012 and Windows 2008 R2). They all exhibited the same behavior.
After checking a few Gen8s we already had installed and up and running, we noticed they were running ILO4 Firmware 1.30. Rolling back the firmware on the new servers to 1.30 gave us desired behavior and the system worked as expected. All our systems are now functioning properly.
Like I said, hopefully this helps someone out there. We spent quite a bit of time trying to track it down.