Here is a great post by Kevin Holman addressing an issue you would come across if you have had to move your SCOM databases or recover them to a new SQL server.

Sample error:

Log Name:      Application
Source:        MSSQL$I01
Date:          10/23/2010 5:40:14 PM
Event ID:      18054
Task Category: Server
Level:         Error
Keywords:      Classic
User:          OPSMGR\msaa
Computer:      SQLDB1.opsmgr.net
Description:
Error 777980007, severity 16, state 1 was raised, but no message with that error number was found in sys.messages. If error is larger than 50000, make sure the user-defined message is added using sp_addmessage.

In essence this happens, as explain, due to the sysmessages being created in the master database on installation. These messages will then be missing after a database move or new sql server recovery.

Kevin has also provided a script to re-add these messages for you here – CAUTION for SCOM 2012 R2 only