To upgrade from 3.1 to 3.1.x using update manager, you must manually specify a new update site.1 These instructions describe how to update from 3.1 to 3.1.x or from 3.1.1 to 3.1.2 only. These instructions should not be used to upgrade from a 3.0.x build to 3.1 or 3.1.1.
In Eclipse 3.1, select
Help --> Software Updates --> Find and Install --> Search for New features to Install
Select New Remote Site.
In the New Update Site dialog, enter Name: Eclipse SDK 3.1.x Updates and URL: http://update.eclipse.org/updates/3.1
Ensure that only Eclipse 3.1.x SDK updates check box is selected and press Finish.
A list of mirrors will appear that have the 3.1.x updates. Select a mirror that is geographically suitable for you and select OK
The update process should now proceed as usual.
1 The eclipse update site is specified as http://update.eclipse.org/updates/3.0 in Eclipse 3.1 features. However, you cannot upgrade to 3.0 to 3.1 using update manager because the startup.jar and eclipse executable were upgraded from 3.0 to 3.1 and update manager does not currently support upgrading these files. If we placed the 3.1.x updates in the standard 3.x update site, this could cause problems for 3.0 installations. Consquently, we have created a new update site for the 3.1.x maintenance streams http://update.eclipse.org/updates/3.1. See https://bugs.eclipse.org/bugs/show_bug.cgi?id=123162 for further details.