That information would lead me to believe there is an issue with your USB data lines. 16.2MHz is almost 2% tolerance, the AVR-USB automatic calibration is supposed to get within 1%. Since the calibration is based on the USB frame clock, a signal problem would result in an incorrect clock as well.
Double-check all of your connections, possibly try resistors higher than 68 ohms if you don't have the exact value on hand. I'm also assuming you have the USB connection correct, but please remember the card edge connector will be reversed from the standard USB pin order. I don't know if you tested the oscillator in a USB port or on the bench.
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