There is a problem with the SelectBox in IceFaces: On a partial submit the submittedValue is not restored. The value is the last stored value (in the model), submittedValue is the user entry.

In com.icesoft.faces.component.ext.HtmlInputText saveState and restoreState are this:
public Object saveState(FacesContext context) {
  Object values[] = new Object[29];
  //...
  values[28] = getSubmittedValue();
  return ((Object) (values));
}

public void restoreState(FacesContext context, Object state) {
  Object values[] = (Object[]) state;
  //...
  setSubmittedValue(values[28]);
}


This part is missing in com.icesoft.faces.component.ext.HtmlSelectOneMenu.

The invalid value (in select boxes) will be reset on the next request (from an other field).

The best solution could be to patch the class com.icesoft.faces.component.ext.HtmlSelectOneMenu.