if it looked fine in iMovie, and in QT it looks pixelated and choppy, chances are it's fine, and QT is playing it with "high quality" turned off (which is the default for some strange reason). If QT actually says the video and audio are different lengths (Movie Properties) and iMovie botched the export, you can fix the sync with
Sync-Hole (choose Match Tracks in the Sync menu). Sync-Hole refuses to scale the audio track, because you should never ever scale the audio track. But in this case, if you are quite certain the audio is the wrong speed, and you are planning to convert again later to {dvd, vcd, mov/aac, whatever}, you might want to use QTPro to extract the audio track, delete it from the original, and Add Scaled the extracted audio to the video. Or use QTMutator to adjust it in place. Once you scale the audio, it will no longer be a an integer multiple of 11,050 khz, and you must resample it (export) to such a sample rate to avoid costly on-the-fly resampling during playback