MIUI 2.9.21 sdcard (external) not detected

Feb 19, 2012
When I connect my Galaxy i9100 via USB to PC the sdcard is not detected (I can see only internal memory).

When I'm in recovery, I can see the sd, which means it is not damaged.

Can anybody help me to solve this?

Thanks in advance

EDIT: don't know what happened and why, but I SOLVED the problem.
Since the Recovery too started saying it couldn' mount the sd (and furthermore it also said that neither the internal memory was mountable...), I re-formatted it via PC as FAT32... It took a while since it is a 16GB card.
BTW, after that I was able to get the sd recognized. Going into recovery, magically I was able to "see" both the memories, internal and external, and to reflash rom.