This is due to a change that Twitter implemented yesterday, retiring their old API (v.1) in favour of a new API (v1.1). Unfortunately, most of the WordPress Twitter plugins still utilize API v.1, and have not yet been updated for v1.1. As such, these plugins have stopped working properly.
We are working to find a solution for blog.ryerson.ca. It is my hope that the developers of the two plugins we use will provide us with quick updates. In the meantime, we have been testing other plugins, in the event that updates aren’t provided soon.
The developers of WordTwit have confirmed that they are working on an update, so we hope to have this plugin updated soon.
We apologize for this inconvenience, and will do our best to ensure this is resolved quickly.
June 13 UPDATE:
WordTwit, the plugin used to send a tweet when a new post is published on your blog, has now been updated. If you were using WordTwit previously, you will need to reconfigure the plugin – it will not automatically work. The new Twitter API has some new requirements, so the setup is a little bit more complicated. Instructions are available in the plugin’s own pages – please read them carefully.
June 25 UPDATE:
The developer of Tweet Blender has recently communicated that an update is in the works, and should be ready sometime next week. We’ll keep you posted!