Url.Action is returning null

What is required to get the various extension methods (URL.Action, Html.ActionLink, etc..) to return a proper URL? Seems that no matter what I pass to these methods, it won't match any routes. I don't get any exception, I just get an null or empty href (depending on the exact method used).

Here's a brief description of the issue in my environment (cut down to show just 1 controller).

I've got the following controller defined...

    /Controllers/Authentication/AccountController

with two actions...

    LogOn
    LogOff

/Routes.axd shows...

routes.MapRoute(null, "Authentication/Account/{action}", 
    new { controller = @"Account" }, 
    new { action = @"LogOn|LogOff" }, 
    new[] { "MyCompany.WebApp.Controllers.Authentication" });

I can manually navigate to /Authentication/Account/LogOn & /Authentication/Account/LogOff and both actions return the expected view.

However, if I put something like the code below into my Home/Index.cshtml page, every single one of the Url.Action calls returns null and the Html.ActionLink calls render an A tag with an empty href attribute.

<ol>
    <li>@Url.Action("LogOut", "~~Authentication.Account")</li>
    <li>@Url.Action("LogOut", "~Authentication.Account")</li>
    <li>@Url.Action("LogOut", "Authentication.Account")</li>
    <li>@Url.Action("LogOut", "Account")</li>
</ol>

<ol>
    <li>@Html.ActionLink("Test LogIn", "LogIn", "~~Authentication.Account")</li>
    <li>@Html.ActionLink("Test LogIn", "LogIn", "~Authentication.Account")</li>
    <li>@Html.ActionLink("Test LogIn", "LogIn", "Authentication.Account")</li>
    <li>@Html.ActionLink("Test LogIn", "LogIn", "Account")</li>
</ol>