Video and Audio Playback issues on Brand New Machine! Advice?

Hi all, I've recently built a new rig, stats as follows:
MB: Gigabyte Z77X-D3H
CPU: Core i7 3770 Ivy Bridge
RAM: 8GB G.skill RipjawsX
GPU: Radeon HD 6950
PSU: Seasonic M12-II Bronze 620w
CASE: Thermaltake Overseer RX-1

I have the system up and running on 64bit Windows 7 Ultimate. I also have an Edirol UA-25 USB Audio Interface running as the pc's default sound device. (http://www.roland.com/products/en/UA-25/)
I have the full K-lite Codec Pack, both 32 & 64bit installed, as well as the latest K-lite update.
I have the most up to date 64 bit drivers possible for every piece of hardware.

Ok, so here's the problem, and this happens with all video formats I've tried so far. (mkv, mp4, mov, avi) When I play a video, every few minutes the audio cuts out for around 1 second. It's almost as if the audio pauses but the video doesn't which then puts the av sync out of whack but as soon as audio starts again the video actually visibly slows down for 1-2 seconds until the audio is re-aligned with the picture, then it plays perfectly for another few minutes. Wash rinse repeat.
I have noticed it does this with mp3 music files too, every minute or so pausing for one second, then resuming play.

I am baffled because my old system ran 1080p video and high quality audio with no troubles, and it was a much less capable machine than the new one.
Old system had same codec packs, same audio interface/driver, same OS.

Any ideas, advice, suggestions etc. would be very welcome.

I will try disabling the Edirol Audio interface, and use the onboard HD audio instead. I'll post back what happens.
My guess/hope is something's not right in the audio department, and the video slowing down is purely a corrective measure for the av sync.
It's worrying that the Edirol driver hasn't been updated since 2009, yet it runs fine on my old 64 bit system.

 

Hi, thanks for the reply and may I say, you have one awesome site here. :drool
It certainly is a strange problem, made even more confusing by the fact that it seems to have fixed itself.
I noticed it was no longer pausing last night, on a .mkv video that always paused about 10 seconds in. Just to be safe I uninstalled the codec packs, downloaded fresh copies and reinstalled. I did notice I originally had the H.264 decoder set to the wrong type for my system. Could this have caused the problem?