Thanks for the screen shot. Very odd. Looked on the site where the Shoutbox comes from, someone else has a simular issue, they logged out of the forum then back in and it worked for them. Odd why this would happen.
Trying to find out if it used Java, cant see it at the moment. No changed been done at this end, but something is a bit screwy somewhere. I will keep digging.
Proved it fails on Firefox, we are running a cut down free version of the Shoutbox.. I have upgraded to a paid version, so will be able to get support for issues like this. The upgrade itself may sort the issue.