I have a book ready to upload to Blurb. InDesign consistently freezes at about 75% of the way through preflight of the pages (cover preflight was fine). I have exported a PDF from InDesign and run preflight on it with Acrobat Pro 10, using X-3 standard, and it passes. Book looks fine in review (Shift-W) mode within InDesign, PDF looks fine in Acrobat Pro 10 and Acrobat Reader. First freeze seemed due to a Running Header text variable box with a specific character style on a non-printing layer. It looked OK but I replaced it, next preflight passed that point and froze on another. Replaced that, preflight froze on next. Latest InDesign CC, Windows 7 64-bit. I've made several Blurb books from InDesign previously, but this is first attempt on a new computer.
Well, it finally thawed. After about ten attempts & attempted fixes, I tried uploading to Blurb one more time, InDesign hung again (Windows Task Manager indicated not responding at 79%) but I was doing other stuff and about 10-15 minutes later, a screen popped up saying the book was ready for upload. I uploaded, have ordered, & hopefully the book will be OK. Still have no idea what was happening, but I guess the moral is to wait 15 minutes, even though Task Manager says Not Responding.