OWA Change Password problem



We are running Exchange 2003 Enterprise fully updated on Server 2003 (also up to date). We recently enabled
the Change Password option and cannot appear to get it to work. When a user clicks on the Change Password
button they get a new window which displays the OWA login page and an error that the user could not be
logged on to OWA. We have a front and back end topology and also use ISA Server 2004. Does anyone have
any suggestions as what might be causing this problem? Any help would be greatly appreciated. TIA
.