Delta_G:
If you really want help fast ( which is doubtful around here with ASAP in the title) then the biggest thing you can do is to help us help you. Don't make it harder than necessary to help you. Go read the "How to use this forum" sticky. Pay attention to the parts about how to post code so it's easy to work with and what sorts of details to include in your posts to get good help. What really separates the wheat from the chaff in this game is the tendency to read the instructions first. It's always the best policy if you want something to work faster.Do you have a code that makes the motors spin the way you want without all the mouse stuff? What does that look like? Do you have a link to the datasheet or some information on that motor shield? Have you looked it over? Does it say anything about what pins it uses? Are you trying to use any of those pins for your mouse?
Thank you, I will make sure to do that next time I post a question! Yes the code that makes both the motors spin correctly is in a .txt file called basic example. This was the original guide that I used to make the robot and the motor shield distributor (It has all the specs in it if you scroll down):
I have looked over this issue, however found no solution as to why there might be an issue. I haven't tried changing the pins on the arduino to see if there may be an issue. However the might be the reason why one motor spins and the other won't.