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If you see this message
This happens when the login page is used and when it is already assigned to an other feature.
To re-access your dashboard, just rename "woffice" as "woffice2" in wp-content/themes/ - that will switch you back to the default Wordpress theme and
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without any data loss.
You can now access to your Admin, then :
- Be sure the "Login page" is not assigned to any Buddypress component in Settings > Buddypress > Pages
- Be sure the "Login page" is not assigned as the front page
You can turn Woffice back on
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and everything
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should be fine 
Let us know if you have any question.