GoPro's website recommends processing its MP4 footage via MPEG Streamclip: "The .mp4 file type produced by the GoPro HD cameras is not supported by Apple’s Final Cut software. The file type is a compressed output format and not an ideal editing format. To convert your files to a more editing friendly format you must use 3rd party software such as MPEG Streamclip (free download)." Or to use GoPro Studio (with its free "remove fish-eye" in advanced settings). I use FCP 7 and I don't see any problem with .mp4. You?