I am seeing the same issue. I have a project with about 50 HDV m2t clips (captured using HDVSplit) and 10 minutes of video on the timeline. It takes about 5 minutes to open the project. During this time, Premiere shows low CPU utilization, but the hard drive is very active. I suspect Premiere is checking all of the files in the project before opening the UI.
The other issue I am seeing is Premiere takes about 2-3 seconds to respond when switching between Windows applications.