Cannot delete user after upgrade to NAV2013

This is after we upgraded from NAV2009 to NAV2013. When we tried to delete a user, it gives error:

Microsoft Dynamics NAV

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The user "FAKEUSER" cannot be deleted because the user has been logged on to the system. You must set the user's state to "Disabled".

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OK

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I changed the State of the user to Disabled and it still gives this error. Interestingly, when I create a brand new user in NAV2013, it does not give this error when I delete them.

Anyone encountered this for upgrades?