WordPress 3.3 is now here. The updated version is better than the old one. However, there are some dew issues which you might face after the upgrade.
One major issue which many people have faced is the problem with the admin bar. There is a common error which many people have reported. Some say that they can not see the Admin bar after the upgrade and others get an error 342 below
wp-includes/class-wp-admin-bar.php on line 342
The good thing is that error wp-includes/class-wp-admin-bar.php on line 342 only shows up if you’re logged in. This means that your visitors will not be disturbed with the nagging error.
How to solve the issues
If possible, you can Re-do the upgrade for 3.3 , it might get your WordPress 3.3 error solved
Check your plugins and see if any are causing conflicts. Deactivate any plugin which might be causing problems.
Deactivating all plugins to see if this resolves the problem. If this works, re-activate the plugins one by one until you find the problematic plugin(s). If you can’t get into your admin dashboard, try resetting the plugins folder by FTP or PhpMyAdmin.
It has been noted that Sometimes, an apparently inactive plugin can still cause problems. Also remember to deactivate any plugins in the mu-plugins folder. The easiest way is to rename that folder to mu-plugins-old
Lastly, it might be a problem with your theme. You can try to change your theme to one which might be compatible with Word Press 3.3. You can also check your functions.php file to check for any compatibility .
Alternatively, you can change your settings not show the admin bar during site view