Text in Illustrator CS6 displays the red plus sign but there is no overset text. How can I remove?

I have some text blocks in Illustrator CS 6 that display the red plus sign that indicates overset text but there is no overset text. It occurs in files that were created with earlier versions of Illustator and now we are reworking them. It can't be deleted. I have cut the text in the box and pasted it into a new text box to no avail. It is not a screen artifact. I have tried copying everything in the file and pasting it into a new file and the little red plus sign comes along. It doesn't print, of course, but is driving me crazy...