problems distilling one particular .book

context

FM 12.04.455 and Acrobat X 10.1.4 – untouched by human hand (or even corporate IT) for at least a year

a .book referencing 10 .fm files and generating a ToC and a LoF

problem

Trying to generate a .pdf (Save as …) is failing, completely and uninformatively. A busy cursor in FM for a while, which then goes away; no sign of life from Distiller, no log file … Not just a network glitch, because this has now happened consistently, several times and across two working days

extra info

All the files in the .book can be saved to .pdf individually

Other .book files can be saved to .pdf

question

any ideas what's wrong?

any tips on how to remedy the situation?

thanks in advance!