This error occurs because the system thinks you are already logged in. To stop this error, your account will need to be made inactive in FocalPoint Admin. To do this:
Log into FocalPoint Admin as an administrator.
Click System Control, Users
In the top left, click the Show Active Users, 3 people icon.
Find and select the user stuck in the system.
Click Inactive, sleeping person icon.
To save, click the green tick icon. The user should now be able to log back in as normal.