Hi Mike,
I have followed the 1.4 manual upgrade process but when I point to /install/upgrade/upgrade.php it is very busy for a couple of minutes, then returns "This XML file does not appear to have any style information associated with it. The document tree is shown below.". Needless to say, nothing works after that point, and I need to reload my files and database from a backup to get back to V1.4.7. I haven't spoken to one person yet who has successfully upgraded to 1.5, and I have about a dozen friends trying to upgrade their shops as well. Can you confirm that you are getting an actual upgrade to work..
Deepesh