3.0 upgrade now my New Post links all show a blank page

Check the Functions.php file for blank lines. Make sure there are no blank lines outside the <?php ?> tags.

I ran into a problem when I loaded wp-admin and wp-includes from the latest build. When you move files about sometimes the file permissions get changed. That was my problem. The wp-admin folder had no permissions for group or world use. I added the r and x permissions for read and execute and I was up and running and able to add posts for the first time in 5 days. Whew! My thanks for the good info in the threads.