I had this problem. But I waited for some time and and then slowly the project opened. I think cs4 loads all program and essentials first and then it starts to look for the media, which is about 90 percent of loading. And also it scans all the drives. What i did is I shifted all the media in the project to one drive and disconnected all ext drives. disabled antivirus, (otherwise it is possible that when premier is trying to access the file, av might want to access it and conflicts and hangs. If nothing works then then best is to import sequence by sequence into a new project and see if any file is corrupted.
I donno how long you waited but its worth keeping it hanging for some more time, without touching the mouse or kbd and see.
all d best