Memory card error with SDHC Extreme 30MB/s, class 10, 32GB, Help please?!

I am working with a JVC GY HM-100 ProHD and above mentioned SanDisk card.

Today I filmed an important event and one of the recorded clips ( 3.71GB in size) give, on camera, the message “Memory card error” and stops playing back. 

(All the other clips -in total 11.33 GB are fine…)

When I try to play back the same clip on my iMac (with Quick Time Player) not only the play back stops at the same spot, but also my iMac freezes and I have to do a hard reboot to get it working again!!!

The same happens when I try to copy the corrupted clip to my iMac ====> copying stops and my iMac freezes!

My questions are the following:

* Could anybody explain this event?

* Do I have to expect more future recording and iMac problems with this card?

And last but not least:

* I there any chance to recover the corrupted clip, the footage is of emotional importance to me!

Thx in advance for any help!

Bets regards from The Netherlands