As previously stated, I have the identical problem lourober mentioned Nov 18 2013. I previously had docs created in Pages 4.3 within iWork 09. After upgrading to Pages version 5.0, the new icon appeared on the dock and when I clicked it, I was able to see all my previous docs. Double clicking on any of these docs opened OK and incorporated the changes included for version 5.0. I was able to close any doc and reopen without any further problem. I then created a new doc under version 5 and saved it. On trying to open it, message stated I needed a newer version of Pages to open it. I then right clicked doc and from pull down menu, selected Open with Pages Default App (5.0), but received same message. If instead I click Show package contents, 4 folders named Data, Index, Index2 and Metadata, plus 3 .jpeg files, namely preview micro, preview web and preview are shown. By clicking on the last preview.jpeg, my file opens and I can read it as a preview file. If I now click on the pull down menu above and select Get Info, a panel appears on the left of my screen showing the general information about my doc, confirming name of my doc xxx.pages, shows the new Pages icon and says open with Pages.app, and finally has myself named with custom access to read and write. Finally, I cleared the new icon from the dock and pulled down the new icon for Pages 5.0 in my applications folder to the dock. I then clicked it and tried to open my new file again, but received the same message as before,"You need newer version of Pages open it."