I'm sure that debugging techniques are in general language independent and there is no such think "C debugging".
There is a lot of different tool that can help you find simple problems like memory leak, or just stupid mistakes in the code, some times it even can catch simple memory overruns.
But for real hard to find problems like problems originated from multitasking/interrupt, dma memory corruption the only tool is your brain and well written code (with thinking in advance that this code will be debugged). You can find more about preparing your code to debugging here. It seems from Sydius post that Apache already have a good tracing mechanism in place, so just use it and add simalar to your code base.
In additional i would say that another important step in debugging is "don't assume/think". Base all your steps on bare facts, prove all your assumption with 100% accuracy before you making another step based on that assumption. Basing your debugging on assumption usually will bring you to wrong direction.
Edit after Dave's clarification:
You next step should be find the smallest part of the code that cause the problem. You sad that if your disable certain section the module is loaded. just make this section as small is possible, remove/moke everything in the section until you will find ideally one line that will cause the module not to load. And after you find this line. it will be an exact time to start using your brain :) Just don't forget to 100% verify that this is the line.
