Bit of a strange one this, as the problem's already been solved; but in such a weird way I had to post to get opinions.
Before I go on, let me assure you that I'm 100% certain of the following events and last time I checked, I was still sane.
So I do a job in Poland; camera passes through airport scanner with 2 8gb P2 cards still in camera. Get back and cards have corrupted; footage is in sync in log & transfer viewer; out of sync in FCP timeline; lose a lot of sleep and ultimately lose client.
Try to use cards again a few times after formatting and reformatting however new footage is still out of sync, seem's like they're permanently corrupted, accept that I'm restricted to using those cards for visuals only.
Fast forward about 12 months after using the cards a few times, still with the same problems and I film a futsal game and use the 2 cards right at the end as I just need visuals.
Whilst editing in the clips; realise the sound seem's in sync, but don't pay much attention as it's a quick edit sound's not important.
Check the other day and the cards are fine, sound is perfectly in sync.