[Exception… “Component returned failure code: 0x80040111 (NS_ERROR_NOT_AVAILABLE) [nsIChannel.contentType]” nsresult: “0x80040111 (NS_ERROR_NOT_AVAILABLE)” location: “JS frame :: file:///C:/Program%20Files/Mozilla%20Firefox/components/FeedProcessor.js :: FP_onStartRequest :: line 1440” data: no]
Line 1440

So what the heck does that all mean?
Basically, there is an exception error on like 1440 of the local Firefox javascript file “FeedProcessor.js”.

The line in question is as follows:
channel.contentType = “application/vnd.mozilla.maybe.feed”;
The whole section of code reads as follows:
// nsIStreamListener

// The XMLReader will throw sensible exceptions if these get called
// out of order.
onStartRequest: function FP_onStartRequest(request, context) {
// this will throw if the request is not a channel, but so will nsParser.
var channel = request.QueryInterface(Ci.nsIChannel);
channel.contentType = “application/vnd.mozilla.maybe.feed”;
this._reader.onStartRequest(request, context);

How to fix this:
This is mearly a short-lived problem thrown by Firefox and can be corrected by clicking “Clear” in firebug and refreshing the current page.
You could always just restart Firefox to correct this as well if you would prefer that route.

This error could have been caused by:
AdBlock Plus
Firefox loading invalid RSS feeds