So I have my own action for key binding Ctrl+Tab. It is assigned to JTabbedPane.
Did you use the proper InputMap when you assigned the Key Binding. Most LAF's will use the JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT
InputMap.
See Key Bindings for a list of the bindings for your LAF.
If the Key Binding don't work then another option might be to remove Ctrl-Tab as a focus traversal key from your tabbed pane:
Set newForwardKeys = new HashSet();
newForwardKeys.add( KeyStroke.getKeyStroke("TAB") );
tabbedPane.setFocusTraversalKeys(KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, newForwardKeys);