There isn't supposed to be a msdb.log file, so that's not the problem. The MSDB transction log is MSDBLog.ldf
Can you do as the message said and check the SQL error log? In object explorer it's under Management-> SQL server logs. There'll be messages in there regarding why the db is not available. Find them and post them here.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability