I ran into identical problems trying to launch Acrobat 5.05 in Mac OS 10.4.7. After wasting a couple of hours, I detached my ethernet cable to disable my Internet connection so that the app couldn't launch the search at the Adobe site. I then entered Preferences>General and specified Manual Checking for updates. I also disabled the auto-update function in my other Adobe products of that vintage. Everything now seems to work properly.