Looks like half the code is missing but I've uninstalled, deleted and readded the module.
Partly sorted it is something to do with Drupal for Facebook module
I'm moving this issue to the IMCE queue as this is about debugging the browser itself, not the editor plugin.
IMCE Wysiwyg bridge only opens the IMCE browser on behalf of the editor.
No in my case it is the Facebook module and that has been confirmed.
Drupal is a registered trademark of Dries Buytaert.