iduino Mega R3 I2C not working

[Randy P.]

I recently purchased 10 Geeetech iduino Mega R3s and am having a problem with them. They run the "blink" program fine, but they do not work with a very simple test of the I2C interface. I have several other Chinese "clone" Arduino Mega R3s as well as a "real" Arduino Mega R3, and they all run my test code perfectly - it simply sends a message via I2C which is received by another device. I have tried 5 of the 10 Geeetech Megas that I just bought and NONE of them work with I2C. I switch back and forth between them and my other Megas, and those work fine. I have tried to re-upload the code many times and am doing exactly the same steps with the Geeetech Megas as I'm doing with my other Megas -- and only the Geeetech Megas do not work. I would be sorry to have to send these back but unless you have a suggestion I think that is my only choice. Please advise. Thank you