Random freezing / lockups

ok.. i built this system about 2 months or so ago.. well everything isnt totally new.. i actually had to come here to figure out my old power supply was bad to get my new stuff working.. anyways.. i ran into problems almost a week ago.. i had my little nephew swap out one of my wireless lan cards... and ever since then ive been having problems with the system locking up.. it even does it in the bios.. i havent really nailed the problem down as of yet.. but sometimes the computer doesnt even want to give me video output or post but when that happens i just stand the video card up straight and pow i got video then i let the vid card go.... im on a breadboard so the video cards will lean either to the left or the right.. even tried wedging something between them so that they are standing perfectly straight up in the slots and that didnt work.. it seems like any component i touch or thump will get the system to post..

ok.. my specs..

intel e7200 it was oc'd to 3.4 but when i started having problems i dropped everything back down to default.. so its at 2.53 now..
xfx nforce 680i lt motherboard.. got this about 2 months ago.. it was a refurbished part.. was working good when i got it..
i have 2gb of pqi ddr2 memory.. its 800mhz and is supposed to run at 1.9v i know this because i had the same sort of random freezes im having now when i tried to run bios defaults and that made the ram run at 1.8...
i have a brand new antec basiq 500w power supply its about a month old..

geforce 450 vid card about 2 months old.. also have a geforce 8800gts as backup.. tried both cards same issue..
i have 2 optical drives and 2 hard drives.. SATA hard drives.. but only the hard drives are hooked up now because my system is on a breadboard...

ive already tried running the system with minimal hardware.. still seems to lockup randomly.. i doubt its heat.. because its super cold out here and i got a big ass hsf on the cpu wit arctic silver.. im leaning toward some kind of short again.. no idea what is shorting it out.. but something has to.. i hope its not the damn psu cuz the thing is brand new.. and im kinda leaning toward it not being the psu because i installed both cards and set one up as a physx processor and it handled them both..

it could be the ram.. but i also doubt that.. although i cant get memtest86 to complete without the system locking up on me..

i honestly think its the motherboard.. because sometimes when i try to boot the system.. all of the text onscreen is garbled and most of it is missing sometimes..

i mean it runs fine until it crashes..

one thing i havent tried was the other pci slot.. maybe my nephew fuxx0red my other one.. and its shorting my system out.. gonna go try that now while i wait on some replies..

one thing id like to note is.. it may mean something maybe not, but when i start system up all the fans are spinning fast.. by the time i get to windows logon and i logon and the fans spin down.. it locked this last time i tried.. so i donno.. i think my motherboard is doing some freaky things to my voltages.. because like i said when i first got this thing it used to do this.. but that was because my RAM was undervolted.. what if my bios isnt actually using the settings im telling it to use? thats kinda what im thinking also.. cuz sometimes when i turn it on.. its like uh.. im in safe mode go check your cpu multipliers and voltages etc..... to my knowledge i shouldnt see that.. that should only come up after an unsuccessful overclock.. ie the system locked up after you put in new settings and the bios just reverts to safemode defaults so that you can fix the prob.. probably gonna try and reflash my bios also..

not to sound weird or anything.. but my pc is my life.. im disabled and this is how i go about my day to day life.. computers! help please..