<p>I'm seeing an ambiguous error in Firebug. I don't think it's particularly related to the script I'm writing, however I don't have enough details to be able to determine that from this one error alone. Has anyone seen something similar and have a suggestion?</p>

<p>error:</p>

<blockquote>
  <p>[Exception... "Component is not available" nsresult: "0x80040111
  (NS_ERROR_NOT_AVAILABLE)" location: "JS frame ::
  file:///Applications/Firefox.app/Contents/MacOS/components/nsSessionStore.js
  :: sss_saveState :: line 1896" data: no] [Break on this error]
  this._writeFile(this._sessionFile, oState.toSource());</p>
</blockquote>

I have run across the same error myself, and it is an internal FireFox issue, not an issue with your script at all.  It is related to the saving of the FireFox state:
According to:
http://blogs.unbolt.net/index.php/brinley/2008/04/26/0x80040111_nssessionstore
, it is caused by a corrupted session state.
In short, I don't think there is anything you can do to avoid it (it is a bug in FireFox or perhaps a plugin).  However, that link claims you can just clear your session (via closing FireFox) to get rid of the problem when it crops up.
FYI, you may want to read the comments, as it seems closing FireFox won't necessarily eradicate the problem... but if all you care about is whether your script is at fault, then don't worry :-)