I've done a tremendous amount of homework on this topic. I never knew there was such a big difference in speed and reliability from one brand of SD card to the next. What I have discovered (and many others have too) is that the fastest and most stable cards out right now are the Panasonic cards. With many of the other brands, they come from a variety of countries: Tiawan, China, Japan, ...etc. Supposedly, the best and most reliable all come from Japan. The problem is, with many brands, you can't tell where the card was made until after you've bought it and opened it. It's my understanding that ALL of the Panasonic cards are made in Japan and have a 10mb/sec write speed. Hope this helps.
The way I understand it, as long as you get one that was made in Japan, you should be fine. The problem is, you won't know where it was made until after you've opened the package and read the back of the card. For example, the back of the package for a Lexar card will say: "Made in Tiawan, China or Japan." So you won't know about that card until after it's opened. Panasonic cards (I believe) are all made in Japan. Plus, they have the fastest write speed out there right now. My Dimage Z1 came with a Panasonic 16mb card, and I've just ordered a Panasonic 256mb.
