Fixed by making RESET button do a server-based reset of the form rather than a client-based one - r3404. Specifically, replaced:

                 <h:commandButton type="reset"
                                  value="RESET" title="Click to Reset All Properties to Their Original Values"
                                  styleClass="buttonmed"/>

with:

                <h:commandButton type="submit" immediate="true"
                                 action="#{EditGroupResourceConfigurationUIBean.reset}"
                                  value="RESET" title="Click to Reset All Properties to Their Original Values"
                                  styleClass="buttonmed"/>

and:

    @End
    public void reset() {
        FacesContextUtility.addMessage(FacesMessage.SEVERITY_INFO, "All properties reset to original values.");
        this.redirect.setViewId(VIEW_ID);
        this.redirect.execute();
        return;
    }

Fixed, rev3416

This bug was previously known as http://jira.rhq-project.org/browse/RHQ-1758
This bug relates to RHQ-1759