One of my keys on my midi controller is not playing. In the transport window when I strike the key it gives a note of g4 but no number associated with it. When I strike other notes it gives a number value associated with it.

hmmm... have you by chance set the g4 key to a command in controller assignments? Cheers Rounik

thats what I think I did, but I'm not sure where to check or fix the problem.

go to: Controller Assignments (CMND-K) You can check in there to see if you've assigned it to another command. Let us know how you get on. by the way, what keyboard is it? Rounik

I hit command k now what? I'm using the o2 8 keyboard.

Hi K1, Check in the different columns (switch to "Expert" tab if needs be) and if you find a command using the G4 key on the O2 then select it and press delete. Let us know how you get on. Cheers Rounik

I'm not finding it

Please try with another software (Garageband for example) to see if your G4 key is working. If it is not working with GB, the issue is with your MIDI controller, not Logic. Tell us how it turns out.

actually my g4 and a4 keys are not working in Logic. They are working in Garageband.

Are you using Logic 7 or Logic 8 ?