2003 Accord 5-speed clunks when downshifting and braking

[technomad]

Hey all, I have a 2003 Honda Accord with a 5-speed transmission. The transmission shifts very smoothly through all the gears; however, as I downshift from 2nd to 1st gear while at the same time braking hard, I hear a clunk under the driver seat. The clunk is only heard as I move the shifter from 2nd to 1st while the brakes are being applied. If the brakes aren't being applied while I shift, the clunk doesn't happen. I assume the problem must be due to some sort of slop in the drive shaft which is made manifest by the change in torque from shifting and the resistance to the torque from the brakes, but I'm quite unfamiliar with this vehicle and I'm not sure where to start looking for the problem. If anyone has knowledge concerning this problem, I'd very much appreciate any input!