I just upgraded from 1.41 to 1.51. I'm using WordPress integration, which has been working just fine.
After the upgrade, I'm getting the following error:
Warning: mysql_connect() [function.mysql-connect]: Access denied for user 'your-mysql-usern'@'localhost' (using password: YES) .....
Fair enough, these settings are indeed not set and do not need to be set, since I'm using Wordpress integration. This is still setup correctly and to verify this, I also deliberately made an error in the integration path variable. I then got the error that it couldn't find wp-load.php in that path, so this seems to be working.
Any help would be greatly appreciated.