Maintenance Cleanup Task fails when executed with SQL Agent but dont if executed manually

Hello,

I have a job that fails with the following error if exectued via the SQL Server Agent but not if executed manually.

The error is:

 Error: 2014-03-31 21:30:14.89     Code: 0xC002F210     Source: Maintenance Cleanup Task Execute SQL Task     Description: Executing the query "EXECUTE master.dbo.xp_delete_file 0,N'\\erpfiles\b..." failed with the following error: "xp_delete_file() returned error 2, 'The system cannot find the file specified.'". Possible failure reasons: Problems with the query, "ResultSet" property not set correctly, parameters not set correctly, or connection not established correctly.  End Error

I have checked and the user configured to run the SQL Agent has all needed accesses to the folder \\erpfiles\b....

Have you an idea to help me go further in my troubleshooting ? Or have you an idea to solve my problem ?

Thanks in advance