Lightroom LR 4.1 RC Flickr publishing broken

Hi there,
I got this weird error message when I am working in Adobe Lightroom. I do not have much knowledge about Lightroom. I am not getting the error message correctly. Is that says a document is empty? I have been working in the document for a week. What might be the root of this error? Please support to find the solutions. Thanks.

Can’t update this collection.
An internal error has occurred: Error
Domain— NSXMLParserErrorDomain Code=4 Line 1:
Document is empty
Userlnfo—0x11201f850
{NSLocalizedDescription = Line 1: Document is empty
}
OK
