had the same problem less than a few days ago. after lots of staring at yhe moterboard (around my soldering) found out my iron touched a random transistor and attached it to a point i made on the pcb board with a MICROSCOPIC bridge of solder.
i figured i was completely fcuked anyway at that point (double-boot and frag with modchip on, frozen startup screen with it off or unplugged), so i was willing to try anything. i stared and stared at the motherboard for at least ten minutes (with no magnifying glass, mind you) and i just barely spotted that solder bridge.
i tapped the accidental bridge with the iron to seperate it, hooked everything back in...ready to go to bed, still depressed that i screwed my box up, and to my immeasurable surprise everything just booted up fine.
flashed the chip in less than 5 minutes, uploaded evox in about 2 minutes, BAM!
our mutual friend Xecuter obviously doesnt have the patience for those who DONT READ THE STICKIES (can't blame him), but he probably frustrated and delayed you from getting your sweet-ass modchip working quickly because of it.
so i'll fill in:
to put it very simply, you either got solder on something you shouldn't have(clumsiness/solder splash), or you broke a trace (the green lines on the mobo got scraped by the soldering iron).
it's really simple to use the search tool at the top of the page. type in "repair" if you need to fix a trace (hope not).
hope i was a little help, as you may be a nanometer of solder away from finishing. if any information i gave was false, or not entirely correct, please step in.
good luck, bud.