Re: Soft flooring???
The squeak is definitely indicating movement, however determining where that movement is can be tough some times. Does the squeak sound like a surface squeak or does it come from deep within the floor? If it's surface, then it's the hardwood rubbing each other, if it's from below, then it's likely joist movement.
Have a helper walk across the area while you're underneath. There should be little to no discernible deflection of the joist, if there is, then Tim's suggestion will likely cure the problem. If there is no movement, then the squeak is likely coming from the hardwood itself.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!