Frame hangs when creating PDF

I'm running Frame 8, unstructured, on Vista. Also running Distiller 8.

I have a book file and was creating individual PDFs of the chapters doing Save As PDF on each chapter. After three weeks of doing this Frame starts to hang when creating the PDFs. Nothing different in the files, just some editing of commas, mispellings etc. Sometimes just repaginating for page numbers. I noticed, strangely, that I first had to delete the old PDF, it wasn't overwritinng. Then that started hanging so I was changing the name of the file. Then changing the name wasn't working. 

Frame was opening Distiller but it wasn't doing anything else. At some point it doesn't even open Distiller. Just hangs Frame. Doesn't matter if I reboot, it has no affect.

Then, doing absolutely nothing, it starts working again ... for a while. There's nothing intricate about these files. They're pretty vanilla. Lots of text, a handful of tables (or not) and some graphics in eps or tif format.

What is going on here?

Dottie M.