I'm having a very similar issue with a 2007 Mac Mini I recently purchased on eBay. When I first received it, the Mini was working fine. I replaced the internal drive with an SSD, installed 10.6.8, booted it up and all was well. My problem started when I tried to use Boot Camp. When I started the process, the Mini instantly rebooted without giving me the option to partition the drive or anything. I exited the Windows installer and rebooted the Mini to try to go back to OS X but it would not boot into OS X and none of the keys would work to enter recovery or choose boot options. I eventually removed the drive, wiped it with another computer and put it back in but that didn't work either. I then went ahead with installing Windows to see if that would allow me to use other boot options but after successfully installing XP I still could not go into recovery mode or choose boot options.