I have been using the arduino mega 2560 with a simple sensor shield that contains a gyro, bma180 accelerometer, and magnetometer that all operate on i2c.
I was working on it tonight and after I uploaded code like 50 times the uploads started freezing mid way giving weird errors like saying its not the correct board ect... Now the only way I could fix this was to remove the wire.h library from the program and upload it. That library is critical to it working....I found out that if I disconnected the sensor shield before uploading the wire.h library could be used. Then I put the shield back on and reset the board...nothing, the program completely freezes. I then tried to burn the hex directly with my mkii and the program didn't freeze instead it had a tremendous delay....then told me none of the sensors could be found on i2c. The i2c line has pull up resistors and a level shifter. It seems as if placing the shield on the arduino totally freezes it.
Strange thing though is that it was working all night before then suddenly a new sketch just froze the entire thing permanently. I've tried talking to individual sensors and nothing its like the entire i2c hardware line on the arduino has been fried or its damaged. I can't see how 4 sensors all suddenly died.
I'm going to desolder all of the sensors tomorrow and manually test them all before I start to entirely blame the arduino I just need to make sure that its not a bug or something within the arduino or ide.