That sounds about right for an e6600 with your vcore. Mine starts to need more than 1.45 around the 3.5ish mark. Most people I've seen with 3.6ghz+ are on water or better, most of the time with 1.5v vcore or more. Some start needing the volts a little higher than others, but I don't see anything unusual about what you're getting. Try 1.475v or something and see, you probably just need a little more juice to go over 3.5 area.
Also, have you checked all the bios settings?
In jumperfree settings:
-Lock pci-e to 100 (raise a tad later if you want), and pci to 33mhz
-Disable spread spectrum
-Make sure mem getting enough volts, strongly recommend at least a couple memtesting loops done on it, once you reach desired fsb.
-On my P5B deluxe, it can easily go over 500fsb with all the mobo voltages (fsb term,nbcore,sbcore,ich) set to auto
. I would set them there whilst finding your max, cause it should work. Set them manually and play with them later. Your call.
In CPU config:
-disable c1e support otherwise vcore will be controlled automatically, I'm sure you have this one set already from your earlier post
-disable vanderpool (virtualization tech) unless for some reason you want it, not sure if disabling this one helps though
In chipset menu:
-I've seen some problems with this mobo and certain ram, most of these problems should be fixed now with newer firmwares. You shouldn't have a problem with those sticks I think, setting the real timings. But I've seen times where people had a hard time figuring which timings worked, or they had to set it to auto, with other sticks. I just don't see why yours would have a problem though, your sticks are almost certainly micron D9 IC's, they should work fine with the P5B I would think.
Good luck with it man, I hope you get higher
Also guys, hasn't this up to 400fsb hole thing been fixed via firmware now? I thought I saw somewhere that it was not a problem anymore. I flashed mine not long ago, but haven't brought the fsb down below like 440 since then really.