This thread has been a godsend for me. Unchecking the "Connected at power on" stopped the hanging when I restarted my Windows XP Pro virtual machine. However, I suspected that the issue wasn't connecting at power on, but the default "Auto detect drive" being checked. I unchecked the "Auto detect" and assigned my CD-ROM drive letter (G: on my Windows 7 Pro host) to be reconnected at power on (I left the "Connected at power on" CHECKED). The restart works every time AND I don't have to manually connect my CD-ROM drive after my VM machine has booted.
Hope This Helps Someone,
Bill Vallance