One problem related to manual transmission has been reported for the 2009 Infiniti G37. The most recently reported issues are listed below.
The manual transmission in my 2009 Infiniti G37s started grinding gears nearly every time the transmission was placed in 6th gear. This resulted in longer than necessary gear changes at high speeds and prolonged time with only one hand on the steering wheel. The car was never driven excessively rough. This problem started at ~6000 miles on the odometer. At ~8500 miles, I took the car in for repair. Infiniti replaced the transmission with a new transmission under the factory warranty at no cost to me.