I am getting a lot of warnings, some regarding my style sheet:
ott 24, 2014 5:16:17 PM javafx.scene.CssStyleHelper calculateValue
WARNING: Could not resolve '-pdfsam-dark-text-color' while resolving lookups for '-fx-text-fill' from rule '*.label' in stylesheet file:/home/torakiki/repos/pdfsam/pdfsam-fx/target/classes/themes/defaults.css

And some not:
ott 24, 2014 5:16:17 PM javafx.scene.CssStyleHelper calculateValue
WARNING: Could not resolve '-fx-control-inner-background' while resolving lookups for '-fx-background-color' from rule '*.list-cell' in stylesheet jar:file:/usr/lib/jvm/jdk1.8.0_40/jre/lib/ext/jfxrt.jar!/com/sun/javafx/scene/control/skin/modena/modena.bss

I have consistent steps to make it happen on my application but I've not been able to create a SSCCE for it. The application layout looks good but the application hangs a little while spitting out all those warnings.
I don't know exactly how to investigate it, is there anything I could verify to understand weather it's a jdk bug or an application bug?

UPDATE:
I finally could spend some time on this and I managed to create steps to reproduce it. The idea is to have two stage, one is the application, the second one contains application log messages added to a ListView either if the stage is shown or not.

public class App extends Application {

private TestListView logs;

public static void main(String[] args) {
Application.launch(App.class);
}

@Override
public void start(Stage primaryStage) throws Exception {
VBox main = new VBox();
VBox secondPane = new VBox();
logs = new TestListView();
secondPane.getChildren().add(logs);
Scene secondScene = new Scene(secondPane);
Stage secondStage = new Stage();
secondStage.setScene(secondScene);
Button showLogs = new Button("show");
showLogs.setOnAction(e -> secondStage.show());

Button addText = new Button("add");
addText.setOnAction(e -> logs.appendLog("MyMessage"));
main.getChildren().addAll(addText, showLogs);
Scene mainScene = new Scene(main);
primaryStage.setScene(mainScene);
primaryStage.show();
}

public static class TestListView extends ListView<String> {

public TestListView() {
setId("log-view");
getSelectionModel().setSelectionMode(SelectionMode.MULTIPLE);
setCellFactory(new Callback<ListView<String>, ListCell<String>>() {
@Override
public ListCell<String> call(ListView<String> list) {
return new TextCell();
}
});
}

void appendLog(String message) {
getItems().add(message);
scrollTo(getItems().size() - 1);
}

static class TextCell extends ListCell<String> {
@Override
public void updateItem(String item, boolean empty) {
super.updateItem(item, empty);
if (item != null) {
setText(item);
} else {
setText("");
}
}
}
}
}

STEPS:
-Click "show" to show the log window
-Click "add" to add a message to the log window
-Hide the log window
-Click "add" to add a message to the log window while it's closed
-Click "add" to add a message to the log window while it's closed

A number of warning are shown:
dic 13, 2014 12:02:41 PM javafx.scene.CssStyleHelper calculateValue
WARNING: Could not resolve '-fx-text-background-color' while resolving lookups for '-fx-text-fill' from rule '*.list-cell' in stylesheet jar:file:/usr/lib/jvm/jdk1.8.0_25/jre/lib/ext/jfxrt.jar!/com/sun/javafx/scene/control/skin/modena/modena.bss
dic 13, 2014 12:02:41 PM javafx.scene.CssStyleHelper calculateValue
WARNING: Could not resolve '-fx-control-inner-background-alt' while resolving lookups for '-fx-background-color' from rule '*.list-cell' in stylesheet jar:file:/usr/lib/jvm/jdk1.8.0_25/jre/lib/ext/jfxrt.jar!/com/sun/javafx/scene/control/skin/modena/modena.bss
.......

This was tested on Xubuntu and both jdk 1.8.0_25 and 1.8.0_40-ea-b11