I recently purchased an HF21 and used it to record a 50 minute musical performance. In the thumbnail preview on the camera, only 1 file appears. However, when the .mts files are downloaded to my harddrive, there are 3 separate .mts files of approx 2GB each. At the file change, there are visible glitches where several frames of the video are missing - I know this because I also shot the musical with my GL2 on miniDV tape. Is there a way to avoid the glitches when the file changes on a continuous shoot? Thanks

Yes - do a search for file stitching programs - there were a couple options, and usually the software that came with the camera can to the stitching without glitching. This is a common problem, discussed a few times here, but it's been a while since it came up.