I was creating a new test blog today and during the install process I ran across a bug. I created a database and a user for the database; however, I did not give the user any privileges to the database so when I went to run the install script on 2.9.1 it threw an error...and a bug
Instead of giving me the message that there was an error connecting to the database, I got a "Fatal error, call to undefined function wp_die() in file wp-includes/wp-db.php on line 1147. This function is defined in the functions.php file but for some reason it is not being registered. I ended up doing a print_r($message) to get the error message and then I noticed that I had not connected the user to my database.
Once I gave the user some privileges, it worked fine.