Serious delay/lag issue

I've been working with premiere pro for about a week now (at work) on a windows machine. I'm working on a commercial where the edits need to be tightly cut to the music. The problem i'm having is that about 3/4 of the time when i press play, the video lags for about a second. It just sits there while the audio plays, then when it starts playing it's out of sync with the audio.
I'm editing on a mixed timeline using raw footage from a 7d and files in the xdcam ex codec (which is decoded with a plugin). This is the first i've done really intense editing on this machine.
I'm also running premiere at home on my mac and haven't had any issues at all.
This is really frustrating, as it's severely slowing my editing down to a crawl because i'm trying to cut to tight beats.

Dell T76000 Dual 8-core 2.4 GHz
NVIDIA Quadro 2000
NVIDIA Tesla c2075
Adobe Premiere Pro CS6
After Effects CS6
Cinema 4d r12

I have been plagued by this same issue on my mac for the last year.

I also use an aja io xt and sure enough when I turned it off. The issue completely went away.

Thanks and any further updates would be greatly appreciated.

Dustin.

Aja ioxt
imac 2012 3.4GHz intel cor i7
adobe premiere cs6
32 GB 1333 MHz DDR3
AMD Radeon HD 6970M 2048 MB
OX X 10.8.2