I just purchased MS Office 2013. Previously I used 2010. I encountered the same problem you described, which I never experienced with 2010...No matter how much I clicked on the text boxes in my document, I couldn't edit the text, or I'd only be able to do so after a really long period of clicking! Not efficient. Anyway, I basically went into the layout box and changed my text wrapping and all of a sudden I had access to all the text boxes in the document. Unfortunately, I wasn't paying attention to what I changed it from, or to, as I was just clicking away and hoping for the best. I went back into layout to see if I could figure it out. A couple times when I chose the text wrapping options 'tight' or 'square' it had the same effect of not allowing me to edit the text. Sorry I can't fully explain but maybe if you change whatever text wrapping option you currently have, it'll work. I also clicked on the options 'move with text' and 'fix position on page' so you could try those also. All the best to everyone having this problem!