I had the exact same issue. I did the usual troubleshooting and found that the new (2.0.65) version of NGG was conflicting with the FeedWordPress plugin I’ve been using for over a year now (meaning I’ve been using the same version). Obviously the conflict (but not necessarily the fault) was with the NGG upgrade. I deactivateded the 2.0.65, uploaded an older version of NGG(v. 1.9.12) from a backup and everything is running fine. After that I just manually deleted the 2.0.65 flies (I didn’t use the “delete” option from dashboard because I didn’t want to risk it deleting files in the database.)
Maybe you can try an older version of NGG, see if it helps your issue.