I have a 43" 7304 currently installed with NVM 0.60 and i also have the 50hz bug. In the NVM files link a couple of posts above there is an update to NVM 0.61 and if knew for sure it would solve this bug i definetely would install it.
Recently i talked to Philips to return it for repair because they did not seem aware of this issue. Later on i received a call from their techinical dept. that it actually is a known software problem that will be resolved by a software update. They wanted to contact me when this update was ready, Well we are waiting for over a year so i think it will be ready soon.....
Are you able to chase them for it, since it has been over a year and they have acknowledged the issue?