Sonar 2.2 & Tascam FW-1884 sync problems?

Hey all,
I see someone else asked a similar question over a month ago and got no replies. Anybody else have this experience now?
I just got this FW-1884 yesterday morning and it seems great... if I could just get it all working! I had it going pretty well on my old Dell Pentium III 550 in Sonar 2.2, but really got it to use with my new VAIO laptop, Pentium 4M 2.2 GHz. Everything looks to be set up fine on this computer, but there seems to be a sync problem. When I record, the result is off by a random small amount, different every time. I tried singing a dorky little vocal ditty and adding a harmony, but the second track would be off. I tried setting up a metronome (out of the 1884 via MIDI port 1 into a keyboard, audio from the keyboard going back into the mixer) and recording it, only to find it out of sync. I tried recording several tracks of the metronome, and it came out slightly different every time.
Is this a latency problem or what? Tascam says it's zero latency monitoring, but a lot of good that does you if you never know where the audio's gonna end up when you record it!
Clock set-up seems simple enough. 1884 set to internal, 44.1 Hz, Sonar set to audio Sync, and 44.1 Hz.
Any ideas?