I am using SpringSource Tool Suite
Version: 2.5.2.RELEASE
Build Id: 201101081000

When I attempt to add a plugin (from help->install new software), I select a site from my list, then I get an alert which says: "Login details were not accepted. Please provide login details for download.eclipse.org"
or the same message from dist.springsource.com if I choose the springsource update site.

I have tried entering guest or anonymous with no password, I have tried my account from the eclipse marketplace site, I have tried no user or password; all result in the same error. If I cancel out of the dialog box it will also fail to connect.

The detail error log says:
Some sites could not be found. See the error log for more detail.
Authentication failed for http://download.eclipse.org/technolo...7/update-site/.
Authentication failed for http://dist.springsource.com/release/TOOLS/update/e3.6.
Authentication failed for http://download.eclipse.org/releases/helios.

Anyone else run into this issue?