Something that can be very frustrating is if your videos for an application are slow loading up. You might be thinking it is a slow server but chances are the meta data for the video file are at the end of the file which means the client must download the entire video before playback can start!
I had this issue recently with an application using FlowPlayer to play tutorial videos.
There is a section on their website about this issue and it was indeed a video converter moving the meta file to the end of the file on me.
A quick fix was to move the meta data back to the start of the video using QTIndexSwapper.