After a lot of search I founded a resolution for this problem.
After I created manually the Desktop folder -sch task finished ok.
http://blogs.msdn.com/b/sqlserverfaq...rver-jobs.aspx
Resolution
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· A “Desktop” folder seems to be necessary in the “systemprofile” folder in the location C:\Windows\SysWOW64\config\ to open an Excel file
· Create the “Desktop” folder for Windows 2008 Server (x64) under the location C:\Windows\SysWOW64\config\systemprofile
· And for a 32 bit Windows 2008 Server create the “Desktop” folder under the location C:\Windows\System32\config\systemprofile