Contextual menu throws exception when interacting with same sub-menu for the second time. Steps to reproduce:
1. launch Modena app
2. scroll down to MenuBar & ContextMenu section
3. open View menu
4. open New sub-menu
5. click somewhere else to close the pop-up
6. open View menu
7. open New sub-menu (exception appears)

Note that when pop-up menus are displayed, they shiver (shadow is blinking).

Here is the exception:
May 22, 2013 8:51:24 AM javafx.scene.CssStyleHelper calculateValue
WARNING: Could not resolve '-fx-color' while resolving lookups for '-fx-background-color' from rule '*.context-menu' in stylesheet internal:stylesheet0.6996794932105632.css
May 22, 2013 8:51:24 AM javafx.scene.CssStyleHelper calculateValue
WARNING: Could not resolve '-fx-text-base-color' while resolving lookups for '-fx-text-fill' from rule '*.menu-item>*.label' in stylesheet internal:stylesheet0.6996794932105632.css
May 22, 2013 8:51:24 AM javafx.scene.CssStyleHelper calculateValue
WARNING: Could not resolve '-fx-text-base-color' while resolving lookups for '-fx-text-fill' from rule '*.menu-item>*.label' in stylesheet internal:stylesheet0.6996794932105632.css
May 22, 2013 8:51:24 AM javafx.scene.CssStyleHelper calculateValue
WARNING: Could not resolve '-fx-text-base-color' while resolving lookups for '-fx-text-fill' from rule '*.menu-item>*.label' in stylesheet internal:stylesheet0.6996794932105632.css
May 22, 2013 8:51:24 AM javafx.scene.CssStyleHelper calculateValue
WARNING: Could not resolve '-fx-text-base-color' while resolving lookups for '-fx-text-fill' from rule '*.menu-item>*.label' in stylesheet internal:stylesheet0.6996794932105632.css
May 22, 2013 8:51:24 AM javafx.scene.CssStyleHelper calculateValue
WARNING: Could not resolve '-fx-mark-color' while resolving lookups for '-fx-background-color' from rule '*.check-menu-item:checked>*.left-container>*.check' in stylesheet internal:stylesheet0.6996794932105632.css
May 22, 2013 8:51:24 AM javafx.scene.CssStyleHelper calculateValue
WARNING: Could not resolve '-fx-text-base-color' while resolving lookups for '-fx-text-fill' from rule '*.menu-item>*.label' in stylesheet internal:stylesheet0.6996794932105632.css
May 22, 2013 8:51:24 AM javafx.scene.CssStyleHelper calculateValue
WARNING: Could not resolve '-fx-text-base-color' while resolving lookups for '-fx-text-fill' from rule '*.menu-item>*.label' in stylesheet internal:stylesheet0.6996794932105632.css
May 22, 2013 8:51:24 AM javafx.scene.CssStyleHelper calculateValue
WARNING: Could not resolve '-fx-color' while resolving lookups for '-fx-background-color' from rule '*.menu-up-arrow' in stylesheet internal:stylesheet0.6996794932105632.css
May 22, 2013 8:51:24 AM javafx.scene.CssStyleHelper calculateValue
WARNING: Could not resolve '-fx-color' while resolving lookups for '-fx-background-color' from rule '*.menu-down-arrow' in stylesheet internal:stylesheet0.6996794932105632.css