It happens the the first time you try to add a new page. then the second time it works without the error. Here are the steps to reproduce.
1. open the portfolio tool.
2. Click " Create a new portfolio"
3. Select "design your own portfolio.
4. Select the Add/EDIT cotent tab
5. Click Select Layout and choose Simple HTML as the default layout.
6. Click Add Page, add some content, and then click the add page buttpn at the bottom, which will return you to the Add/Edit content page.
7. Click the Save changes button. Page should change okay.
8. Now repeat steps 6 and 7 to add a second page. You'll get an error when you click Save changes.
9. Now return to the presentation and repeat steps 4,6, and 7. This time you can save your changes.
10. Now repeat steps 6 and 7 to get the error again. So, you can only click saev changes once. the second time, you'll always get the error.