I am working on a zimlet that adds some buttons on the fly, basically stealing from the salesforce zimlet (thanks Marc). The following works fine in FF, but not IE. Furthermore, it only seems to fail when the page is refreshed.

  //NOTE:  Op SETUP defined earlier
  this._quickOpDesc = ZmOperation.defineOperation(null, ZmOperation.SETUP[ZmOperation.NEW_VIDEOMAIL]);
  // Get the mail toolbar
  this._mailCtrl = appCtxt.getApp(ZmZimbraMail.MAIL_APP).getMailListController();
  if(!this._mailCtrl._toolbar) {
    // initialize the mail list controller's toolbar
  // Best I could figure out in the debugger
  this._mailToolbar = this._mailCtrl._toolbar[appCtxt.getCurrentViewId() || 0];
  // Insert buttons into the mail toolbar
  ZmOperation.addOperation(this._mailToolbar, this._quickOpDesc.id, this._mailToolbar._buttons, 2);
In IE, this._mailToolbar ends up undefined. I think it has something to do with the way this._mailCtrl._toolbar is declared as an empty object (in ZmListController:
	this._toolbar = {};		// ZmButtonToolbar (one per view)
...yet later treated as an array...
this._toolbar[view] = new ZmButtonToolBar(...)
IE doesn't seems to not want to reference the contents by an index. Of course, since it is impossible to see what is going on in IE, who knows.

Any ideas on this?