exmh with mozilla-firefox

When I have firefox already running, then executing

    'mozilla-firefox <some url>'

will open up a new tab in the existing browser.  I'm trying to
configure a similar behavior in exmh.  To
configure exmh for the behavior I want with Opera, specifying
this in ~/.exmh/exmh-defaults works:

*uriMosaicApp:  opera
*uriNetscapeCmd: \
	opera -remote openURL($xuri,background-page) -display :0.1 -nosession

In the exmh GUI "*uriMosaicApp" is the "Mosaic program name", and
"*uriNetscapeCmd" is the "Netscape command".


When I specify the "Mosaic program name" as "firefox" and the
"Netscape command" as "mozilla-firefox $xuri" then I get the
firefox pop-up window saying:

    Firefox is already running, but is not responding.  To open
    a new window, you must first close the existing Firefox
    process, or restart your system.

I've been told that firefox syntax would be:

    mozilla-firefox -remote "openURL($xuri,new-tab)"

When I use that syntax, then the xterm where I started exmh displays 
this message:

    Error: No running window found

When I leave off the double-quotes in the config, then I get the 
firefox warning about an already running firefox.  Likewise, I
get that error when I leave off -remote.  --display-":0.1" doesn't
change the behavior.

For what it's worth, I'm using firefox 1.5.0.3 with exmh 2.7.0.

Does anyone know how to get firefox to respond correctly to clicking 
on a URL in exmh?

Thanks much....

--
Kevin