Hello,
Please try deleting the preferences.
On what operating system are you?
To delete the preferences please follow this instructions:
Close Cubase.
Click on the menu "Go" on the top tool bar of your mac.
Press the option key of your keyboard, that will show the library menu within the contextual menu.
Click on Library.
Search for the preferences folder.
Inside the preferences folder you will find the Cubase folder.
Drag and drop the Cubase 6 folder into your trash can.
FINDER > Go > Library > Preferences > Delete the Cubase folder
If you need more information please read the knowledge base article bellow:
Best regards,
GN