Uploading of this kind of file isn't allowed!

I can create create a directory with mange files but if i try to upload a file i get this:
Uploading of this kind of file isn’t allowed!

What am I missing?

thanks

Check that the file type is allowed by going into the Manager.
Tools=>Configuration=>File Manager=>Uploadable File Types

Also check the user’s permissions in the User tab of the user editor pane.

Fixed

Go to security tab, manage users, click on user, click on user tab:
Uploadable Image Types: Use System Configuration Setting