The problem is that the file allocation table (of sorts) is corrupted. Things like this can happen to any hard drive device, so to fix it, you must treat the karma as an external hard drive and proceed from there.
Connect the karma to your pc with the usb cable so that windows will recognize it as a device (assigning it a drive letter) and you can access it through my computer.
If you can't access it through my computer, then use [[start>settings>control panel>administrative tools>computer management]]. Use the disk management tool to find the karma and give it a drive letter.
Then you should run data recovery software on that drive. The software will ignore the file allocation table and read through your hard drive sector by sector to determine what is actually on the disk. One data recovery software that I am using is by a SalvageData Labs. Yes, you have to purchase salvage software (or acquire it by some means), But it’s a nice software I am sure you get your data back.