The problem here is the memory card. Although memory cards do not have moving parts like a good old hard drive, it can still be damaged through drops.
Whenever I disconnect a usb storage or sd card from any android device without unmounting it first I get the same exact error as the OP. If you never disconnected the card physically then the problem is with your sd card or something small in the connector. If you're card is corrupt, have errors, or any problem like that then it can crash, causing you to get that error. Although a reformat can solve your problem temporarily, it will not save it forever. Once you get errors on a memory device you need convince yourself that storage device will soon corrupt (hours, days, weeks, months, years).
If it happens with all the cards you have used, different brands/size/speed, and you don't drop your phone then the problem may lie with the physical connection with the card and the phone.