possible bad BIOS reading (kinda sucks), or possibly your mobo is overvolting (not much of a problem)
In BIOS set it to 1.575v...does the actual voltage reading change to ~1.65v? If it does it's a simple overvolting mobo, and you just have to take that into account when setting the voltage. overvolting is MUCH better than undervolting IMO, cuz you actually have a wider voltage range up top, stead of having to run 1.675v to get a measly 1.63v.
If it does not help, and still reads 1.72v...i would blame a bad voltage regulator or possibly a bad BIOS. Try flashing your BIOS and see if it helps, and see if anyone else has this problem with your perticualr mobo over at www.google.com