The brake and fork could be at a natural resonance frequency.  Like if you shake a bus pole at just the right frequency you can get it to shake.  Is there any play in the headset or brake?  You can try shortening the pad.  Give up cantilever brakes for a cyclocross means it road bike.  And you need to change out the levers to go side pull.

Front wheel shudder on Cyclocross brakes
If a cancerous tumor has a lot of mutations in them why can't the immune system detect them? If a person has cancer could this somehow alter the person's immune system so it doesn't function effectively to detect greatly mutated cells? Does the fact that a tumor is 'made' of 'mutated' non-foreign human cells help it to be undetectable?
