Index has no root node

[jlbarrera]

When i try add a new category:

Please correct the errors below then click New Category.

    * A system error happened during the operation: Index has no root node. Check that the correct index locations are being used.
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What's happened?

Thanks!!

[jlbarrera]

Problems with my database. The version of database was diferent of the version of alfresco software.
So i delete the database and i start Alfresco, and all work fine.