After a distribution upgrade from Natty 11.04 to Oneiric 11.10(currently on development branch), the first things I do is to install the gnome-shell which is being the best fix from 11.04 version. Yes! It is a Gnome 3 shell which able to work side by side with Unity(the default desktop for Ubuntu).
The most important, bad and pain in the ass things i found out that Gnome 3 on Ubuntu 11.10 not working is the Run Shorcut Keyboard Key. By default, the Alt+F2 will bring this run window up, but somehow in 11.10, it did not do anything.
So this is how to fix this problem. Go into Activities menu on the top of left panel on your desktop to bring out the menu, the simply type the word 'keyboard'. It will return a few result, but click on the menu located in settings section where the icon of keyboard and named as 'Keyboard' to bring up a keyboard setting popup.
From the keyboard settings window, navigate to Shortcut tabs and set the System > Show the run command prompt key with Alt+F2. To set the key, simply double-click on the list.
That's it! I hope you will enjoy the run command prompt as much as I do.