FireFox focus() returns error

[pipjockey]

I am working on a page that is nearly 100% generated by Javascript
code. I have the page operating in IE,Opera,Firebird,NS under
Windows without errors. When I recently downloaded FireFox, it
reports the following type error message in the javascript console
window:
--------------------------------------------------------------------
Error: [Exception... "Permission denied to get property
XULElement.selectedIndex' when calling method:
[nsIAutoCompletePopup::selectedIndex]"nsresult: "0x8057001e
(NS_ERROR_XPC_JS_THREW_STRING)"
location: "JS frame::http ......myURL,file,method,line# "
data:no]

Source File: .... Line: ....
----------------------------------------------------------------------

This error is generated when I explicitly call a focus command such
as:
document.getElementById("r4c1").focus() ; where "r4c1" is the ID for
a input element of type "text".

The error message is not generated if I tab to the input element or
simply click on the element, only when I attempt to direct focus to
the element. Focus is shifted correctly, my complaint is the message.

Any suggestions to either an approach to correcting the anomaly or to
handling the exception gracefully would be appreciated.

pip