It sounds now as though it may be a resource issue, are you trying to preview the movie as it is d/l. Or is it a complete movie.

Are you also d/l while trying to play the movie.

What does your task manager show for CPU & RAM usage when this happens.

Also does your CPU have HT technology and if it does are you using it. This normally needs to be configured in your bios setup.

It doesn't seem normal that task manager takes that long to come up without it being a possible resource issue.