problem: If the height of a dialog box is larger than the height of the browser window the dialog box will still center vertically causing the dragable title bar and close box to be above the viewable window space and inaccessible.

solution: Limit the top position of a dialog box to 0. Browser windows scrol downwards, not upwards.

Potential code fix within the this.open function in ui.dialog.js would be to add around line 124:

if( top < 0)
    top = 0;