HELP: Keyboard/mouse unresponsive during Startup Manager (HD select)

Hello everyone,

I am having an issue on my 1,1 Mac Pro. I have 4 HDs in this, one of them being a Windows disk. I was in Windows and wanted to restart back into Snow Leopard, but once the boot selection screen came up, both my mouse and keyboard became unresponsive. I was able to hold down Alt. to initiate the boot selection screen, but not anything after that. I tried unplugging my keyboard/mouse and plugging them back in, but still nothing.

I simply CANNOT select the boot disk I want because I cannot use my mouse to select it, nor my keyboard! I tried to boot regularly, but it's defaulted to Windows for some reason, even though my Mac drive is in drive bay #1. What could be the issue here? And how do I make Windows not think that its drive is the main boot drive?

EDIT: I tried again, although this time I unplugged an external HD I had connected temporarily; I also tried holding down the Alt. a minute into the boot manager. This time I was able to use my keyboard, however my mouse was still unresponsive. Any ideas still?

Thanks,
-MDD