There can be a number of factors that may cause YOUR movie to glitch, if its just a web download, aside from your hardware or any catalyst settings.

Better to create a small file yourself in FCP in the the correct codec and at the corect frame rate for the desired output device you will be using.

I can send you a demo movie if required for testing - but first - can you confirm your setup, output device and refresh rate (led / projection etc) and required format and frame rate...

When playing content with audio - catalyst prioritises the audio (if set to 'play audio' playmode). You should set the playback rate to match the movie.

For best results on 'most' systems - you should ensure that your movies are rendered as 'Apple intermediate Codec' (AIC) at the required frame rate (eg 25 or 30fps) and that you playback from a Solid State Drive (SSD)

Do contact me if you require further help /info

Simon