False Triggering I/O

I have a circuit with 2 PIC's that are communicating via discrete I/O. Outputs on the first PIC are tied to inputs on the 2nd PIC. Some of the lines are triggering when an i/o line next to it comes on. I tried pull down resistors on the output side of the line (not sure if that would help or not...but it doesn't seem to do anything). All this is happenning on my test board and was wondering if maybe it has something to do with that. I was hoping someone could give me some circuit tips that will help to eliminate this problem.

what about your codes???

If you post the emitter and receiver ones, we can help, unless... would be really hard and do some assumptions is not our cup of tea in many case

one solution that might not be gereally accepted. refere to the picture i posted.

do the wiring for each input