Hi Michal,

Which dataflash chip? What does your spi code look like? Do you have a 2.7V part with the proper level changers to the rest of your circuit? When you write to the part are you checking the status register to make sure the operation has completed before trying the next operation? Have you read Atmel's apnotes concerning these parts? (for example, AN-4 and AVR335). Have you read and reread the datasheet which describes all you need to use the part?

Dennis