MIDI to Audio Sync Problems

Hello all, I have a quick question concerning syncing MIDI and Audio.
 
First off, I am recording a Korg M50 that is going stereo into a Cakewalk UA-25EX. The UA-25EX is set to record at 44.1kHZ and is plugged into my laptop with the included USB cable. I am using the drivers included with the UA-25EX and am recording into Sonar LE. The laptop is a Compaq Presario CQ60, Windows 7 64 bit computer with an Intel(R) Celeron(R) CPU 900 @ 2.20 GHz processor and 2GB of ram.
 
Now I am a lousy drummer so I was hoping that I could us SI-Drums to drum for me. The problem I am running into is that I can put drum loops on the SI-drums track, but when I go to record and play with the metronome/drums with my Korg M50 (Audio track now), on playback my playing is no longer on the beat with the SI-drums even though I was playing on time with the drums and metronome when I was recording.
 
So how do I get the drums and my recording to be on time with each other both during recording AND during playback?
 
Thanks in advanced for replies.