The PlayStation 4 launched back in mid-November and had sold extremely well with very little issues, but in that time, an error has been causing problems in some consoles over time according to the official PlayStation forums. This data corruption error is said to not only cause lost progress, but also has made some games and systems unplayable.
The problem identified as ce-34878-0 Error has brought 34 pages of comments on the PlayStation forums since launch, so it appears to be more than an isolated issue. Most cases involved the inability to play certain games, but some systems wouldn’t let any applications run at all.
There have been many recommendations to this solution, such as deleting of your save files or replacing your console. However, Sony has yet to speak out on this issue in detail.