My experience is similar to yours...CFS following viral infection which never cleared up, but pre-existing stressors were probably more important. Dealing with the stress, allowing my body/brain to heal, then slowly building my life back up again resulted in complete resolution.
If you look at how the brain works, there is quite a lot of evidence pointing towards chronic stress resulting in CFS-like symptoms. I suspect the culprit is the "central governor" region of the brain (which is involved in central fatigue).