This is usually caused by missing taxonomies that are used in a menu, but do not exist anymore.
You have a couple of solutions to try, but do not forget to always create a backup of your files and database before you try any of them.
**Method 1**
Remove the taxonomy items from the menu
Delete all session data, cookies etc...
Method 2
Find the table wp_term_taxonomy in the database
Find a record called nav_menu
Delete that record
Method 3
Find the table wp_terms in the database
Look at the different terms and decide which ones you do not need
Delete the terms you do not need anymore
When none of these solutions, or a combination of the solutions work, please let me know. You have still a couple more options, but those are a lot more destructive.
source: http://stackoverflow.com/a/33753824