The reason is the following: The symptoms are that when the eval board comes up the I2C looks at address A2 or A4, and when the customer design comes up the I2C looks at A0, which is invalid. The 24C02B does not use A0, A1, A2, meaning there is no internal connection, so any address supplied to the EEPROM chip is viable. On the other hand the 24xxxx uses these pins and these pins must be physically tied to address 2 (A0=0, A1=1, A2=0). If this is not done than the chip will not accept the data packet. Verify that you have connected A0-A2 on the EEPROM before trying to write data.