Having sync problem importing Reason audio file

I'm doing collaboration with a friend in Idaho and I'm in Washington. I have a quad processor, 4gb ram, win 7 64 bit, Sonar 8.5 Producer version and my friend is using Reason 6.0.1, win 7 64 bit, 8gb ram.

I recorded some tracks at 126 bpm, 44k, 24 bit and sent him a mix at the 44/24 resolution.  I used a click to record my tracks and sent him a mix that was selected with Snap to Grid on set to Measure so he could paste my mix into Reason and play to it. There was a drum track included in the mix which another friend played and sync'd perfectly with my tracks, but no click. The drummer friend uses Cubase and I had done a similar remote transfer with him successfully via my ftp site. 

My Idaho friend imported the file into Reason and played a bass part with it. He then exported the bass part out of Reason at the 44/24 resolution which he also recorded it at. He uploaded the file to my ftp site, I downloaded it and imported it into my Sonar project which is the same resolution 44/24. When I imported the bass track into Sonar the audio on his bass track didn't line up correctly with mine and it actually was longer by a couple of seconds judging by the last note of the tune. The bass part by the 5th measure is slightly off (late) and at the end is a couple of seconds off comparing the last note that we should be hitting together.

He sent me a mix from Reason and the bass is sync'd up perfectly on his mix with the original mix I sent that he imported into Reason. I would like to do the mixing with Sonar at my place.

It seems like a clock issue but I'm not sure how to troubleshoot this or what a solution would be. Please let me know if you have any suggestions on how we can troubleshoot this problem or ideas for solutions.

Any help would be very much appreciated,

John