Connect to LocalHost Error

Actually "Can't connect to localhost" is not a network error-- that is, it does not refer to problems with communication between your desktop machine and GridRepublic nor between your desktop and project servers. This error refers to an "internal" error-- a failed connection between the user interface of your desktop app and the core computing program (the two are actually separate programs).
In most cases, one of these simple options will solve your problem:

• Reboot your computer

OR

• Try clicking "Advanced", "Select computer", leave both boxes blank and hit OK

OR

• Try clicking "Advanced", "Select computer", type in localhost, leave password blank, click OK

OR

• Try clicking "Advanced", "Select computer", type in 127.0.0.1, leave password blank and click OK)

...And if none of the above work, your best bet is to upgrade to the latest version of the desktop application. If you are currently logged in, you can get that here: Login (or click "home if you are already logged in), then click the "My Computers" tab, then the "Add" button, and then "Get It Now!"