Sonar 7 Producer - Problems sharing CWB files

I'm trying to share a CWB file with someone. We both have Sonar 7 Producer. He is saying he had to click on the file 3 times before it would open and then he got a corrupt file message and Sonar crashed. I downloaded the same file from the file sharing server and it worked just fine on both of my computers. I am running Win XP SP3, and he is running Win 7 64bit. Could the different operating systems have anything to do with it? This is a fairly simple/small file with 2 audio tracks (no effects) and 2 MIDI tracks running through the TTS synth. I have shared very complex bundles with another friend before with no problems whatsoever. Does anyone have any ideas what the problem could be? Thanks in advance for your help. Bassguy59