Did you try to wait for at least 3-4 minutes? Furthermore did you try to do anything else on the computer while poser was loading? I just ask because it happens, that my poser slows down on startup when loading this file. In these cases I go take a break, coffe and cigarettes, then come back to a well booted poser. Still I believe, that poser caches or someway stores the library structure and content.. maybe by indexing... if somehow that file gets corrupted because of added content, the thing might freeze. You could try adding elements one by one, to see which one causes this.