"FAT-fs: IO charset iso8859-1 not found" error while mounting FAT Drives

Apparently, your kernel somehow has problems (maybe a bug). Since there is an updated version available, install it (version 3.11.0-13-generic)

sudo apt-get install linux-generic

now reboot in your new kernel.

I had the same problem a few days ago with 4.4.0-57. modprobe nls_iso8859-1 threw an error, and without that module, that "IO charset not found" message appears.

Turns out the root filesystem was damaged. After a thorough fsck and reinstalling of the kernel (forced with apt-get install --reinstall), that module loads again, and I can mount my USB sticks.

@larskholte Even if the update to 4.4.0-57 fixed your problem by replacing the bad module, be sure to fsck your filesystems! That module not loading is only a symptom of a much bigger problem.