Question : database backup

I am trying to create maintenance plan automatic 1 database backup
I got this error

TITLE: Maintenance Plan Wizard Progress
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Create maintenance plan failed.

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ADDITIONAL INFORMATION:

Could not load type 'Microsoft.SqlServer.Management.Smo.Agent.JobBaseCollection' from assembly 'Microsoft.SqlServer.Smo, Version=9.0.242.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91'. (Microsoft.SqlServer.MaintenancePlanTasks)

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BUTTONS:

OK
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Answer : database backup

>> and stops at this for one hour

do you have any major application running in your server..
Do make sure that SQL Server is not accessed by any applications while you are applying SP3.