I to bought so called Sandisk Extreme II SD cards on Ebay, turned out to be counterfeit and we lost a lot of what should have been precious holiday pictures. This was last year before the price crash and I should have known better they were too cheap!
Now using Transcend Hi Speed cards, brilliant and some good deals, no problems with this supplier competitive to boot and 24 hours delivery.
http://www.mobymemory.com/High_Speed...mory_Cards.asp
Stewart