Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
RIP Ping , Apple Set To Bury Ping In Next Major iTunes Update
Sources close to the company say that Ping, which still exists today in iTunes 10.6.3, will be gone with the software’s next major release, likely scheduled for this fall. And at that point Apple’s social networking offerings will shift to Twitter and new partner Facebook entirely.
Apple launched iTunes Ping on the 1st September 2010 and it never really took off. It was set to be a music social network and a recommendation system