I've opened up an popup window in Joomla 1.5 using modal.js. It is a SqueezeBox. I am attempted call close this popup on popup content but can't.

In Chrome it have an message

Uncaught TypeError: Cannot read property 'x' of undefined

Squeezebox attaches a detailed() approach to the div container with id 'sbox-window'. Out of your modal content find this element and execute close().

If using default modal method (Modal content received through ajax and injected into the DOM).

document.getElementById('sbox-window').close()

If modal is within a iframe

window.parent.document.getElementById('sbox-window').close()