For such an overclock on an i7, you may need more cooling than a Artic Freezer 7 Pro. The freezer 7 pro is rated at 130W and that is the MAX TDP of the i7 at stock speed. So when you start to overclock it you draw more power and create more heat, so really the Freezer 7 pro may not allow 4Ghz on an i7.
The i5 on the other hand has a MAX TDP of 95W at stock speed, so i have a good deal of headroom for an overclock.
All is not lost though.
Try setting the CPU core voltage manually. You’re at 1.32V at the moment.
Take it down a step at a time, until it becomes unstable, then take it back up a step or two until its stable.
To check if it’s stable, Prime 95 is a good check. If it will run Prime for 20 minutes you can be pretty sure the PC is stable for normal use (although overclockers will demand 24 hours).
Here is my bench.
Intel core i5 @3.8Ghz
GFX: ATi HD5770
4GB of Geil 2133Mhz DDR3 RAM (dual channel).