I am trying to create a trade book, 6x9, 144 pages, paperback, and pre-flight says my cover dimensions are wrong. The message is: [Cover PDF] Page 1: Invalid dimensions, got [12.569 in x 9.250 in], expected [13.750 in x 9.861 in]. My cover dimensions are correct. It looks like Blurb thinks I want a hardback cover. I tried three times and each time I get the same message. I used this same cover on an earlier version of the book a few weeks ago and I didn't have this problem then. Any ideas? Is anyone else having this problem?