I'm using token [term] to generate node title ([term-raw] get same error).
When I create node, select taxonomy term and post the node it's shown with empty node title. When I edit this node and post it second time (without changing anything - just reporting) it will be generated correctly. Just the first time I create any node of this type it will be without a title.
It's not to big deal, but nodes without titles could behave quite oddly with some modules, like for example pathauto.