There were earlier versions of WordPress prior to 3.1 that created non-unique GUIDs in the post table. The bug that initally caused this problem is fixed, but the bad data persists in many WordPress installs. The CF GUID-Fix plugin can be run to fix the non-unique GUIDs in the post table. NOTE: After GUID Fix has been successfully run it is not recommended to run the plugin again, and it should be uninstalled from your plugin directory.
If you used WordPress 3.0.x or earlier on your site, you will need to run the GUID-Fix plugin to fix potential bad data that might prevent RAMP from working correctly.