I'm having the same issue on LinkedIn where my WordPress posts do not show up. I've had a WordPress blog on a GoDaddy-hosted site for about 5 months. The Publicize plugin worked fine at first but now it seems to work sporadically for sending my postings to LinkedIn. Today it did not work.
I deactivated the only plugin I had on the list, Better WP Security, with no success. I am able to successfully access the XML-RPC file.
All of my plugins are up to date. I'm using the Twenty Twelve theme with no customization.
Any suggestions?