[list=][*]Upgrade OTRS[*]Uninstall MasterSlave[*]Install OTRS Master Slave (>= version OTRSMasterSlave-1.2.6)[/list]
DO NOT DELETE MIGRATED FREETEXTFIELD12 as this video describes http://www.youtube.com/watch?v=uiXu7tgSdfI
Currently there is an issue with the upgrade path for MasterSlave. If you upgrade an OTRS 3.0 system to OTRS 3.1, and have been using MasterSlave per default setup, the free text field and key 12 will be migrated and flattened to a text field, whilst being marked invalid. This will break functionality in systems where the users depend upon this.
Pelease go here for more updates.
Bug 8388 has been added to the database
In the meantime, a workaround would be great, if anyone can document this.