"Start Inking" button in Word 2007 does nothing

When I write papers on my tablet PC I occasionally switch to tablet mode and use ink to create my revisions. Sometimes, however, I open the inking ribbon and click "Start Inking," but nothing happens. I have puzzled with this for a long time, and came up with some workarounds, including copying the body of my document into a new file (I incorporate my actual changes in a different window and throw away the inked document anyway). But as it turns out, there is a slightly better solution. Apparently, the problem comes from page numbers. If you have page numbers, you cannot "start inking." If you remove them, you can.

Another howler from Word 2007. Why can you not ink when you have page numbers? Why do you get no response from the button instead of an error message?