Long and short: Yopu probably used some unsuitable recording settings or the file uses a custom, optimized CoDec as so many screen capture tools do. Similarly, the data could be choppy/ damaged due to disk performance issues during recording. It may need to be mangled through an external converter to turn into something PS can swallow. Without specific info like what tool you used for the capture and its options it's impossible to tell, though.
Mylenium