revGoUrl and IE 5.1

[RGould8 at aol.com]

There's something fishy going on with the way revGoURL works and Internet 
Explorer 5.1 on Mac OS X:

With IE 5.2 or 5.2.3 set up as the default browser, this revGoURL command 
works fine:

revGoURL "file:///Users/test/Desktop/FIOS_8_2g/DATA/HTML/fiosbiz.htm"

However, if the user has IE 5.1 set up as their default browser, Revolution 
fails to launch the browser to the locally-stored html file.

Any idea what could be causing that?   Is there a unix call I could use 
instead to get around this problem?