Of course "post your code" is the usual mantra but there is a point here when there are hundreds or thousands of lines of code, multiple modules, etc. Might be a bit much to expect people to wade through.
What I usually do in such a situation is start paring down the code to the bare minimums, find the smallest (or reasonably small) program that still exhibits the symptom.
Sometimes the problem is discovered along the way, and if not, I have a much more concise program that I can post!