Just to say we've tried the following things:
Formatted the card with various file system types and re-copied the ML software onto the card. We've also used the EOSCARD bootdisk utility.
My camera was working fine with magic latern up until August. Now everytime I plug an assortment of sd cards no LCD and LED. Only until you remove the battery and the card and re-insert the battery only, does the camera become operational, but of course, with no card to save pictures to.
We also spent some time on various blogs and consulted the troubleshooting guide to try to understand whats going on and whether the boot flag can be reversed in order to restore the camera, I'm guessing this is likely to be the problem.
Apologies for the rocky start, I'm just at my wit's end with this.