I have found that whenever I insert a table into a Personal Book, I get this warning. The book LOOKS fine, but I wonder if I can or should do tables in a way it doesn't complain.
I'd say it's probably an overzealous PB compiler. The final (hidden) cell in a table row is the end-of-row marker and it is zero width. It's what you select when you want to insert a new column before it (i.e., after the last visible column). I'm guessing that's what the PB compiler is giving a warning about, but it's utterly harmless. I wouldn't worry about it.
This is an old discussion, but FYI, the solution is in the Logos Wiki.
Go to Table Properties and set a value for the Preferred Width.
http://wiki.logos.com/PB_%E2%80%93_Warnings_$26_Errors#Warning_caused_by_Tables
