I connected an oscilloscope to the crystal and it shows a nice sine wave at 16.00MHz:


This is of the D+ and D- on the serial line (sending '1'):
D+:

D-:


This is of the USB power - I'm unsure if this is what a 'clean' power source looks like but it was constant like this:





Thanks
BS

 

I ended up installing a ferrite bead on the line and the power looks like this: