I have the I2C (SMBus) working properly in this uC and have a VB GUI which can communicate over USB (using USBXpress) and do I2C transactions from the uC to a separate IC. The problem is that I am having the uC poll a register on the IC every 1s. When I do an asynchronous GUI I2C transaction, every once in a while, I believe it collides with the polling I2C transaction and all the I2C data gets shifted at the GUI (i.e., register 0x00's data shows up on register 0x01) . The I2C data in the IC looks correct (by spying on the I2C bus with a LA). What exactly is happening and how can I fix this?