I booted to a flash drive Tuesday and installed CentOS 6.2 on the internal hard drive. The BIOS is set for IDE mode. Installation was going without a hitch when I left for the evening - the CentOS installer was happily downloading packages and installing the OS.

Wednesday I was not in the office and a coworker shut down the machine, which was on the CentOS installation screen - the machine would have rebooted to the flash drive when it was done installing, since the drive wasn't removed.

Thursday, I come in, remove the flash drive, and try to boot. I get this:

Reboot and Select proper Boot device or Insert Boot Media in selected Boot device and press a key
I get the same message if I try to boot off the same flash drive that worked on Tuesday.

I have built many systems over the years. This has me at a loss. I have to say I'm enjoying the UEFI interface though!