The wire library works mostly, there is a standard I2C scan routine that has been around for a long time. It is very useful in debugging I2C projects. As soon as the scan routine is called, I can no longer talk to the I2C device
The scan code can be found at http://todbot.com/blog/2009/11/29/i2cscanner-pde-arduino-as-i2c-bus-scanner/
On the uno32, I can send data to an I2C device, on the mega, I cannot
It is important to have the jumpers correct on the uno32
I've done some testing and I don't know if theres a fundamental issue here, or at least one different than on the arduino code as I can recreate the same problem with this code on an Uno board with a wiichuck (another of Tod's projects and code).
What I believe is occurring is the scan is freezing a device on the bus. You never know what writing 0 to the device will do, most likely the slave device is looking for more data. I was able to alter the code to send good data to my device (data 0x40 and 0x00) and did not see this lock up under arduino or chipkit.
Do you have example code to demonstrate?