This is an Adobe distiller limitation. TrueType (.ttf) fonts in XPP are converted to t42. If the .ttf font has more than 16,000 characters in it, Adobe Distiller will have difficulty and may fail.
To address the issue you can use one of these methods:
- use Ghostscript distiller, this is delivered with XPP and does not have the same limitation
- use Direct to PDF (divpdf)
It may also be useful to try the .otf version of the font instead of the .ttf. Once the .otf is acquired, run Font Copy to copy it into place and update the font path.