All users receive the following error when attempting to log in to Console:
"Buffer cannot be null. Parameter name: buffer"
This error can occur if the tps_attachment_data table has been truncated. To confirm this run the following SQL script against your Service Desk database:
SELECT COUNT(*) FROM tps_attachment_data;
If this SQL statement returns "0" then this is the cause. This table stores all the attachments saved in Service Desk and it also stores images used within Service Desk.
Restore the database from backup.