Recorded audio is not playing back in sync with other tracks

[ATLracing]

I recently purchased a copy of Pro Tools 11 (the student version) and a Native Instruments Komplete Audio 6 interface. When I purchased the equipment, I intended to record guitar/drum/bass/piano tracks, then master them and have decently professional sounding demos.

As soon as I finished installing the software and setting up the hardware, I immediately tested it by attempting to lay down a guitar track over a drum sample that had come with Pro Tools. Unfortunately, upon playing back the recorded mix, I was surprised to hear that my guitar playing sounded off time with the drums. Thinking that my playing must be a little rusty, I attempted multiple times to rerecord the part with tighter rhythm, but even though my guitar playing sounded perfectly in time through the monitors as I played, when I went back to listen to the recorded tracks, they were always off time.

First I suspected that latency was to blame, but I got my system running with a 64 sample buffer and a total round trip latency of 10.2 milliseconds (as measured by a Centrance ASIO latency tester), which is about the time it takes sound waves to travel 12 feet at sea level and shouldn't be significant. Even when I turned on direct monitoring (which should have almost no latency, the problem persisted). Not only that, but I could easily play along with the tracks on time while recording. It was only when I went to play them back that I could tell they were out of sync.

So, I'm wondering why my recorded tracks aren't syncing properly. Do I need to calibrate something in Pro Tools? Any help would be much appreciated.

Thanks!