Context Menu is not working in Firefox

I have been using dhtmlx pro 1.6 for a long time. You guys did a good job. I just upgraded my firefox to 12.0 and the context menu is not working. In chrome, it works.

I have isolated the failing code in (dhtmlxgrid.js)

/**

  • @desc: called onmousedown inside grid area
  • @type: private
    */
    this._doContClick=function(ev){

el.contextMenu=this._ctmndx;

somehow the contexmenuobject is not being assigned to el.

Please, provide a complete demo.
We may try to find the reason of the issue but unfortunately version 1.6 is no longer supported, so we can’t promise, that the issue will be fixed.