Sorry for not just looking down at your sig. Hmm, mbm5 can be off or atleast the motherboard voltage sensors it reads them from can be off alot. I have had mbm5 readings of my 5v at 4.8v and my 12v at 11.7 or so and get a multimeter to measure every molex lead and also measure the 20 pin atx connector and fine the psu is putting out dead on 5v and dead on if not a tiny bit over 12v on the 12v rail also. Possibly some of your surface mount voltage regulators and such on your motherboard are getting to hot? I have seen that lower cfm around the cpu area because of watercooling can cause voltage regulators ,caps etc to overheat and cause a voltage drop. Maybe feel around, ofcoarse ground yourself, and see if anything like that is hot. You could cut up tiny pentium heatsinks and stick them on with your favorite thermal adhesive. Sometimes that is enough and you can gain 0.1~0.2v if not a bit more depending on what rail it is on as i have seen. Hopefully that is enough, maybe see how hot your north bridge chipset is? as that can help warm up components around it. Hope this helps out, there are other things you could do like connect the 5v or 12v to 5v converters to your mobo but i havnt used those and i havnt worked with that ...yet but i figure you know what i am talking about so just do a search on google or in this forum.