Unable to edit steps of SQL Server Agent job

I developed and successfully tested a SSIS package on a server running Windows Server 2008 R2 Standard and SQL Server 2008 R2 Standard. Having deployed and scheduled the package to run as a scheduled SQL Server agent job using a proxy account, the job's first run failed. I could see from the log that this was due to a failure to decrypt sensitive information from the package's XML file.

I realised my mistake was that the proxy account did not match the account under which I developed the SSIS package so I created a new credential and associated proxy account. My problem came when trying to edit the step in my agent job (in order to change the proxy account that it runs under). I get the following error:


TITLE: Microsoft SQL Server Management Studio
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Creating an instance of the COM component with CLSID {AA40D1D6-CAEF-4A56-B9BB-D0D3DC976BA2} from the IClassFactory failed due to the following error: c001f011. (Microsoft.SqlServer.ManagedDTS)

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ADDITIONAL INFORMATION:

Creating an instance of the COM component with CLSID {AA40D1D6-CAEF-4A56-B9BB-D0D3DC976BA2} from the IClassFactory failed due to the following error: c001f011. (Microsoft.SqlServer.ManagedDTS)

I am therefore unable to edit the job step and the only option appears to be to delete the agent job and start again. Can anyone please shed any light on why this error is occurring?

Thanks.