I'm no WC expert, but I'd say the excessive length of tubing and the fact that the radiator is laying down and in a spot with no airflow, is your cooling problem. That, and your horrid wire management.
Make sure speed stepping is off in the BIOS, and then increase FSB until it is unstable. Then, raise the VCORE by one increment and raise FSB until it is again unstable. Rinse and repeat until you're no longer stable by VCORE alone, and then come back. Also, stop VCORE increasing at around 1.375V - 1.4V, you really shouldn't need that much for 4GHz.
Also, turn your memory divider/frequency down so that it doesn't get overclocked as well. You should be able to hit 4GHz without too much problem.
Make sure speed stepping is off in the BIOS, and then increase FSB until it is unstable. Then, raise the VCORE by one increment and raise FSB until it is again unstable. Rinse and repeat until you're no longer stable by VCORE alone, and then come back. Also, stop VCORE increasing at around 1.375V - 1.4V, you really shouldn't need that much for 4GHz.
Also, turn your memory divider/frequency down so that it doesn't get overclocked as well. You should be able to hit 4GHz without too much problem.