Try with a live distribution and make a disk copy. The bug seems in EXT4 (so the filesystem), so any action you will do, it could make you to lose more data and files.
Check the hardware (e.g. with memtest). Once you rules out this, check if you have installed some modules outside your distribution. If you have no external module, make a bug to your distribution.
Unfortunately, your kernel is tainted (you used a non approved module, probably from your video card), so you cannot get full support from EXT4 maintainers (the bug seems in such subsystem), but you can try to remove such modules, and see if the bug come again (and so you can report it).
On EXT4 bugs there is not much you can do. You can eventually try a older version, or try to repair the filesystem (using a live distribution or a rescue "disk").