XUL on FireFox

[Paul Thompson]

I am getting an XUL error in Firefox. I don't really understand the
error, it is obscure, it occurs only in FireFox, yadda yadda yadda.

I can find the error. I can identify the data structures. I check the
data structures, they are fine.

Is there some resource available which will help with such an error?

Here is the specific error:

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 ::
https://secure.biostat.wustl.edu/haltpkd/java/mainjava.js :: nclkH ::
line 292" data: no]
Source File: https://secure.biostat.wustl.edu/haltpkd/java/mainjava.js
Line: 292