DH here on Sarah's computer...
Nothing has changed on our side of the street, and the software version hasn't changed with the chat software vendor, so I'm wondering what the problem could be.
Do you get any error message? What version of Java are you using? What browser? What operating system?
It sounds like you aren't the only person having problems here, but when I go to the parachat website, I don't see many people reporting problems recently.