I've been having no end of problems with SD cards as well, and have permanently destroyed two so far. SOmetimes, a card can appear to be fried, but can be recovered using a desktop machine with a card reader, by fdisk-ing and reformatting. I've recovered two SD cards this way (aside from the two I blew up). So I guess I'm running 50-50.
Originally, I had the same trouble as you -- an SD card would work for a little while before becoming corrupted. I came into the habit of issuing "sync" commands regularly and this no longer happens to me -- however, now I'll get SD card corruption if I leave the Z suspended for a long time (overnight will do it). This occurs without fail, every time.
I have no other solutions, but this problem is a showstopper for me -- it renders OZ useless for my purposes. I'm hoping that the next release will fix this.