Built-in SD card reader listed as a drive, but won't mount

[Brance]

When I plug in an SD card (actually a micro SD card in an SD card holder) from my camera into the built-in reader on my laptop, the drive is listed (as 'Generic- xD/SDMMC/MS/Pro'), but the card can't be mounted.

If I plug it into a USB card reader then it works no problem. It I plug it into an adapter and then into my Android phone, no problem. It's also accessible on other machines running Windows - and, of course, on my camera.

Any ideas on how to fix this would be welcome.

[valtam]

Can you work with the SD card under Menu, Settings, Disks?

[Brance]

Can you work with the SD card under Menu, Settings, Disks?

No - under 'Volumes' it says 'No Media'...