Yeah I have a Kemco 8MB memory card (Kemco's accessories aren't necessarily the best) and I've had it for the past 5-6 years, and only two files have ever become corrupted on it, both due to either my stupidity or my guests' stupidity. So I'm pretty lucky too.

If this problem persists you might wanna get a new memory card. If that's not what you wanna hear then I'm sorry, but I don't know another way to do it.