I couldn't get my Mac Pro to display the start-up drive dialog when I did the option key trick on reboot. Nor could I get it to boot to the DVD drive with the C key. I pulled all my various peripherals and voila, it worked. I slowly reintroduced connections until I found the culprit.
My Euphonix (now Avid Artist) MC Transport which connects via the ethernet port was somehow getting in the way. As long as I keep it powered off during the boot, the start-up options will appear rather than freezing up.
SAMDOG Digital Post
Mac Pro 2.66 12-core 16gb ram • FSI LM1760W Monitor • Matrox MX02 • Caldigit HD One 8tb Raid • Euphonix MC Transport • Final Cut Studio 3 • Premiere Pro CS5