I have made a test page that works fine
http://www.uk-mkivs.net/test.asp
<%
response.write("no session.lcid set: " & formatcurrency("19.99") & "<br>")
session.lcid = 2057
response.write("session.lcid = 2057: " & formatcurrency("19.99"))
%>
v. strange!!
Anyone know why you need session.lcid in config.asp??