I will try to guess... After RGH, Xbox boot's fine without HDD and DVD... It won't glitch if you have connected DVD drive or HDD, or even both of them.
So... problem is in wire placement. Try to route them in different way.
If you have used alternative soldering points, then lead wires under board (there are small holes to lead wires to boards buttom side).
If you have replaced resistor (SMD replaced with BIG one) near HANA, then try to place it away from HANA chip (as far as you can... small wires helps). Resistor can be hold near video connector (isolated from "world")... about 2 - 3cm far from HANA
------
Please post some pics and more info, next time... or, if this didn't help....