Hi, I also got this message and it frustrated the **** out of me. I double-checked every page in Preview and followed the advice given by others with a similar problem. I found there are a variety of reasons that the default text sign can arise and you will have to work through each solution until you hit on the one that applies to your project.
1. Cross reference each page in your project against the Layout option. You may find that eventhough you have not included a caption at the bottom of each page in a text frame, you have used a frame around your photo that includes text. If you look at your layout page you will note that the No Text box has not been selected. You will need to re-choose the layout page of your choice with the Text box clicked. This will cause your frames and caption to disappear. Don't panic! Just re-selcet the caption frame and yoyr text will reappear.
2. If you have no text in the text frame at the bottom of your page make sure you have deleted the "Insert your text here" notification so the space is blank.
3. The other tricky thing is your photo captions maybe bumping in to the blank text caption at the bottom of the page. re-position your photo caption up or down to clear the blank text frame.
4. If you still have the problem you may have inadvertently made two or more libraries. This means that you have done all the right things to the project you are working on but when you try to upload the computer goes to the default library and tries to upload the unedited version. To see if you have multiple libraries hold down the option key and click on the iphoto icon. If this is the case, you will need to Choose the right library to upload the edited version.Hope this helps.