Those 2 points on the LPT/SPI connections I presume? Yeah those were a PITFA when i tried them. Best to heat the pad from underneath using the iron with a bit of leaded solder on the tip.
Then push the leg of a spare resistor through, it seems to be the only thing sturdy enough to actually go in with any ease. Really though, you can just wire the ground coming from the cable to any ground on the 360 motherboard, or just solder it to the metal casing.