Whenever I try to open one particular file in FCP I get the error message: "file error: 1 file(s) recognized"
however the clip plays back fine in the camera. All other clips from the same shoot are behaving normally.

I've tried opening the file with FCP 7, VLC, Quicktime, Compressor and MPEG Streamclip, but with no success.

Can anyone suggest a way of saving this file?

(BTW, using a 16gb Transcend Class 10 card)

I am not a Mac person but I do know that there were problems with the HM100 files and Macs thatvwere fixed with a software intervention. "Calibrated Software" has such an animal.

Calibrated Software (http://www.calibratedsoftware.com)

Try playing the file back from the SD Card using MpegStreamclip. If it crashes out at a certain point, try exporting before and after the corrupt point of the clip (use In and Out points).
Worth a try - Good Luck.

Charles