Audio sync not consistent in FCE4.0
I have a copy of Final Cut Express. I am using a Zoom H1 as an external audo recorder in conjunction with a Canon SX30is. When I attempt to sync the audio in final Cut Express, the begining of the clip remains in sync however toward the end of the clip, the audio and video goes out of sync. Is there anything in Final Cut 4 that I can do to remedy this?