Unreadable USb drive

this is third time that my computer have failed to read the USb drive.
well actually it reads the USB but not able to open it.
i had same problem with IBM flash drive.
it was working fine one moment then when i tried to use it the day after, it is there in my computer but when i try to access it, pops out message box saying insert k: (my usb drive). i had to ask for A/S. my data inside were all lost. then few day asfter i got it back it happened again. so i had to buy another USB drive. this time sandisk. it worked fine just until last week. this have happed again. now i’m thinking it’s not the usb drive, but my PC or me.

can anyone please tell me what is causing this? what am i doing wrong? and possibly how to fix my usb drive.