While the error message (Figure1) suggests either it’s a trusted location/ security issue, the entry on the Application log of MOSS (Figure 2) clearly indicates that it’s a trusted location issue only.
One or more of these actions will fix this error.
1. Add the document library where the excel report exists as a trusted location (very obvious).
| UI | Central Adminàyour SSP>>Trusted File Locations>>Add Trusted File Location |
| stsadm | stsadm -o add-ecsfiletrustedlocation -ssp ssp-name -location docl ib url –LocationType SharePoint-IncludeChildren True – Description desc |
| UI | Central Adminàyour SSP>>Excel Services Settings>>Add Trusted File Location |
| stsadm | stsadm -o set-ecssecurity -SSP ssp-name -FileAccessMethod UseFileAccessAccount -RequireEncryptedUserConnection False -AllowCrossDomainAccess True -AccessModel TrustedSubsystem |
3. Verify that the Process Account is correctly set-up. To view the process account navigate to Central Admin>>Shared Services Administration>>hover around your SSP and select Edit Properties from drop-down>> Scroll down the page to see the Process Accounts with access to this SSP.
4. When you have more than one Shared Service Provider (SSP) configured on the same server, make sure the web applications are associated to the correct SSP. This is because different SSP’s may have different trusted locations. Web Applications associate to the default SSP when they are initially created. So before you create a Web Application, set the desired SSP as Default using either one of these methods.
| UI | Central Admin>>Shared Services Administration>>Change Default SSP |
| stsadm | stsadm –o setdefaultssp -title ssp-name |
Benny Austin 
Thanks for spending the time to describe the terminlogy towards the newbies!