With the update of iTunes to 10.0.1, it's now possible to "ping" that track, film or program you are listening to or watching from within the music library. Unfortunately this new feature disables the arrow links that, when clicked, takes you to the iTunes store or to the artist or album selected. Disabling the Ping link and re-enabling the old link requires you run the following commands from the terminal:

 defaults write com.apple.iTunes hide-ping-dropdown -bool TRUE
 defaults write com.apple.iTunes show-store-link-arrows TRUE 

If you wish to have those link arrows go to your library rather than the iTunes store run the following command:

 defaults write com.apple.iTunes invertStoreLinks TRUE

After running any of the above commands, restart iTunes and you should find the arrows are back and the Ping button has gone.