MASSIVE lag >.<

[Treifla]

uggggg, i just don't get it.
I have windows 7 64 bit
i have an AMD athlon x4 64bit quadcore at 2.7Ghz
a Radeon XFX HD 5770 XXX
4 GB of 1066Mhz ram (G.skill Ripjaw)
and many MASSIVELY laggy SC2 games.
i will describe this is full, because i have not found a similar problem on the internet after almost a week of searching.
every once in a blue moon, my game runs GREAT. my system can support  everything maxed without breaking a sweat, i know this from the few  very rare moments when it actually works. most of the time however i  get the worst (and most signature) lag.
i will use my roomate as a comparison, he has a system comparable to  mine, plays it perfectly every time, we use the same torrent to play  the game (i gave it to him on my flash drive). differences is, he has  intel, i have AMD, he has Nvidia, i have ATI. we have the same copy of windows 7, once again, he got it from me.

when i get my lag, the video lags like crazy, when i check my FPS,  it goes from 0 to 70ish, then drops back down to 0 again. (my roomates  stays at constant 25 to 45, making me wonder if there is a problem with  the Vsynch or something) sound is what makes it all funny. it won't  play any background music when it's lagging, and sometimes it will  repeat the same sound byte over and over again for anywhere from 10  seconds to 2 minutes.
things i have done.
i have clocked my video card back to normal
i have wiped the drivers and loaded brand new ones
i have wiped the drivers and loaded old ones
i have had my roomate install the game (his worked)
i have closed everything in the background
i have checked my temps with SIW (30c processer, 50c video card)
i have changed the game from using 4 cores to only using one, then two, then three, then all 4 again.
i have prayed to dark and dangerous gods.
i have uploaded all of the latest AI etc.
i have even been considering calling blizzard support lol.
i have wiped and uploaded audio drivers
if you folks have ANY idea whats going on, please help me out, i  just want to play the damn game in between exams, instead of studying,  i have been spending all my time trying to figure this problem out  >.<

[darkshark]

what kind of audio device do you have? is it the default on board kind or an actual card. What kind does your roommate have as a comparison.
Have you checked resource manager for anything?
Are there any errors in your event viewer related to video or sound at around the same time that it lags?

[Treifla]

what kind of audio device do you have? is it the default on board kind or an actual card. What kind does your roommate have as a comparison.
Have you checked resource manager for anything?
Are there any errors in your event viewer related to video or sound at around the same time that it lags?

i am using an onboard card from the ASUS M4A77TD motherboard with up-to-date VIA audio drivers. he is using the onboard card from his Commando motherboard.

i have not checked the resource manager or event viewer, would it be possible to elaborate on those?

[Treifla]

okay, i have solved this issue much by accident,

when i was trying to play, i stood up and knocked my mike out of it's jack and BAM, runs perfectly.

put the mike in, lag, pulled it out, perfect, in lag, out perfect.

i guess this would explain vents laggyness as well.