I cant beleive with all the threads on the P8P67 problems people are still a)buying them and b)posting yet another thread about the same old issues - just take a look through this section its packed with threads about exactly these issues...
What bios is it on? No doubt a pre-release 0402 or first edition 0804. Both are horrendous. Even the more current bioses suck badly with regard to bugs and issues but are at least usable.
Upgrade you're bios to a current version, clear the cmos (best to remove the battery and power cable and leave it for 10 mins with those old bioses, i had issues with it failing to clear aswell)
Also worth ignoring the manual about which memory slots to use (it says A2 and B2) and just go with two sticks in A1 and B1.
You should at least get a bootable system then. If you're memory is corsair XMS3, make sure you manually set "command rate" to "2T" under memory timings, my P8P67 always choses 1T on auto and results in awful stability.
I hope you get it sorted soon but please take a look through the mountain of other threads about these issues, all have lots of good experiance and may help you're specific situation.
edit: Unless you're PSU is faulty, 650w is more than enough. I've had my i7 2600k, 12Gb ram, 3 drives and a GTX470 all running fine on a 600w OCZ supply. I may be pushing it a little as its all oc'd and remember you're GTX460 uses a damn site less juice than the 470.