how can i recover corrupt .mov files that quicktime does not recognise?

we recently 'lost' a whole day's footage by accidentally deleting it. in trying to recover these files we have used many different programs and have had odd results.... sometimes the data is recovered and shows only thumbnails but not the proper film and othertimes says tht quick time cannot open the link because it doesn't reconise the codec. these clips were filmed with a Canon SLR camera and we have searched the reformqatted sandisks as well with the same result.... quicktime does not recognize the file.

any thoughts? it would be a tragedy to lose this footage... well not really, but you know - a whole day's work!

thanks in advance for your help.

Gabi