Have you got the latest updates from adobe?
You are most likely trying to load a file that uses an unsupported codec.
To check if Premiere is broken - Try creating a video in Premiere, say the inbuilt adobe 10-1 countdown and render and save it out.
Then try loading *that* file and see if that works OK and get back to us.
Also try loading the tutorial files that come with the program when you bought it, if those don't load something is wrong.