Speaker crackling problem - firewire interface

Hey guys,

Haven't posted on here in forever but here we go:

This past week I noticed my speakers starting to get a crackling sound when I played any sort of audio on the computer. This happens everytime I turn on the computer now - starts out perfectly, then, over the course of a few hours, the sound starts to crack and I think it even slows down the sound at some point because some songs I listened to randomly changed keys...

I uninstalled/reinstalled drivers, checked drivers to make sure they were up to date (they were), switched ports/cords, nothing. Googling this problem didn't help either :/ so that's why I am here. I didn't touch anything on my computer so I don't know why this is happening.

Some specs/other info:
I am using a FP10 (firepod) firewire interface which hooks up to a firewire card - no sound card is being used. All firewire stuff.
The FP 10 has outputs to a stereo power amp thingy (unsure of the real name of it) and from there the speakers are hooked up.
HP desktop... maybe 2-3 years old. Windows 7, 4 gigs ram. Not sure what other relevant info I can give there.

Thanks

Issue eliminated by restarting the computer or persistent after a reboot?

yes and no. my sound starts out fine after every reboot and gradually gets worse over time. when i restart it does the same thing. every time.

edit: now it seems to go back forth between working and not... blahhh

any ideas? i have googled this forever and everyone has a variation of this problem but not my exact problem.

possible causes:
-could be heat (not probable because it's winter and my room is always cold)
-could be onboard soundcard - not possible because the firewire bypasses all of that, right?
-too many programs/processes running - i am running less than i have been in the past
-drivers are old - everything is up to date, i even uninstalled my firewire ones and put them in again

again, my sound starts to slow down or "stretch" itself randomly. doesn't matter if i am running one process or 100. it just all of a sudden gets worse and sometimes it gets back to normal, other times it doesn't.

UPDATE:
i think i fixed it. i just ran some disk defragger jaunt and deleted a lot of crap in various folders. things are running more smoothly now. i also messed with the settings on my presonus firepod a bit.

Yeah its difficult on such an old machine... but make sure your sound card is furtherest away from GPU and CPU as possible to reduce the chance of interference.