My PC doesn't see my Sandisk Extreme 32GB but my camera does

I bought Sandisk Extreme 32GB SDHC class 10 card. Had no issues for about a month. Few days ago I was shooting some video with my Sony NX3 video camera and everything was a usual, till I got home and try to copy video files to my PC. When I put SD card into card reader, suddenly drive letter was wanished from file explorer. I pull out the SD card and drive letter was back. I tried again and same situation happened. Then I try to connect my video camera with USB cable and everything was OK untill I insert this SD card into the video camera. Then my camera was wanished from file explorer. I try to play those videos into the video camera and every file was there and plays smooothly inside video camera preview. Only workaround I find helpfull was to copy inside video camera all those files from that SD card to another SD card. Then, that another SD card I insert into the card reader and everything was OK. After I assured that every video is OK, I did a format  problematic SD card inside camera and everything passed OK. Then, again I try to insert that problematic SD card into the card reader and same strange situation happened again. I put back that card into the video camera and try to record something and everything was OK. Try to playback that video inside video camera and everything was OK also. Again I try to copy that new recording to my PC and same situation happened again. I forgot to mention that I try to copy files from that problematic SD card in four different PCs and laptops and everywhere was the same - drive letter was wanished as soon as I insert SD card into the card reader. Then I go to my friend and we try to use that SD card in Nikon D5 and inside camera everything was OK. We did a formatting, shot some pictures, pictures was there, but as soon as we tried to copy thos pictures from SD card to PC - same situation…

Any suggestions?