Try booting under Boot Camp, axing Parallels Tools and then restarting and running your Virtual Machine. In case this doesn't result in a resolved issue please give booting in safe mode one more shot - the F8 key actually should work during boot. Keep in mind that it is necessary to use Fn + F8 on some Macs, and if that results in no joy see if you can just send the keypress via the Virtual Machine => Send Keys menu option.