SignalR Stops Working After A While

For some reason, SignalR will just stop calling client methods after a short period of time (about 1 hour or less I estimate). I have a page that shows Alerts... a very simple implementation. Here's the Javascript:

$(function () {

    // enable logging for debugging
    $.connection.hub.logging = true;

    // Declare a proxy to reference the hub. 
    var hub = $.connection.alertHub;

    hub.client.addAlert = function (id, title, url, dateTime) {
        console.log(title);
    };

    $.connection.hub.start().done(function () {
        console.log("Alert Ready");
    });
});

If I refresh the page, it works again for about an hour, then will stop calling the client event addAlert. There are no errors in the log, no warnings. The last event in log (other than the pings to the server) is:

[15:18:58 GMT-0600 (CST)] SignalR: Triggering client hub event 'addAlert' on hub 'AlertHub'.

Many of these events will come in for a short while, then just stop, even though the server should still be sending them.

I am using Firefox 35.0.1 on Mac and SignalR 2.0.0.