Table of Contents crashes on update

I am running InDesign CS4. I have a book file with 5 files, most of which use a data merge. I have a Table of Contents that I processed successfully until today. I wanted to include a new paragraph tag in the TOC. Each time I try to do so, InDesign crashes. I do not use preferences so wasn't sure if I needed to clean out those settings and not clear how to do that. I tried exporting the TOC file to an IDML, but still have the same problem. Any help is appreciated.