I just now noticed that every last file of my GT680W can't be open and view.
I tried all the media software on my computer, and they all say that the file is corrupted or that they can't read its format.
There is a way to watch these videos, or is it a lost case?
If you have one important MOV movie i think you can fix it.
Otherwise like said, your dvr battery is finished and every last file will be corrupted because they are not closed properly.
If gt680 has option to shut down camera immediately try that, i don't remember what kind of menu options gt680 has.
Otherwise you have to replace dvr battery.