Hi,
Sentivity to load caps greatly depends on the actual crystal that you are using. I found out that the crystal manufacturer engineers are often very helpful with this kind of situations. They can also tell you if the soldering process that you are using can be the source of the failure.
From my experience, the oscillator isn't that sensitive to the load capacitor value, but if you use a value that is already on the edge, it is still possible that the stray capacitance of the PCB makes the oscillator unstable.
Good luck,
cyberblak