My friend recently had the same problem with his Accord. Originally we just thought the linkage was binding inside the door but later we found it was actually the latch mechanism. This is something you could yourself because its all about how much time do you have and how good you are with the tools. If I were you, I would pull the passenger seat from the car so that you can get full access to the entire door. You dont have to remove the seat but it would give you more room to work. Next roll the window down and pull the small plastic cover on the other side of the side mirror. Next you need to remove the door trim. You have to remove the screw hidden behind the door handle and the one in the arm rest. Next you have to pull the door panel off carefully so you dont damage the plastic clips. Start from the bottom up. Once all the clips are loose, push the panel up to clear the window ledge. Roll the window back up. Now you have to carefull peel back the plastic from the door and now you have access to the whole locking mechanism. If you are lucky its just something loose that is causing the linkage to bind. If not then you might have to replace the latch which would require you to get the door open and unscrew from the door jam. My buddy had to pry the latch box open from the inside to manually release it so that he could get the door open and unscrew it properly. Hopefully you wont have his kind of luck. If this sounds too much then I would suggest seeking the help of a shop.