This happens when trying to install any role or feature on Windows 2008 Server. Here's part of my session log.
32084: 2010-03-23 14:21:40.227 [ServerManagerCmd] Running with the following arguments: '-install backup-tools'
32084: 2010-03-23 14:21:40.617 [LoadExtensionAssemblies] No extension assemblies registered.
------
'WindowsServerBackupOptionalComponent', guest: 'CommandLineTools', guest deleted?: False
32084: 2010-03-23 14:21:51.677 [Provider] Begin installation of 'CommandLineTools'...
32084: 2010-03-23 14:21:51.693 [Provider] Install: Guest: 'CommandLineTools', updateElement: 'WindowsServerBackupCommandlet'
32084: 2010-03-23 14:21:51.708 [Provider] Installation queued for 'CommandLineTools'.
32084: 2010-03-23 14:21:51.833 [CBS] installing 'WindowsServerBackupCommandlet ' ...
32084: 2010-03-23 14:21:51.833 [CBS] CreateSessionAndPackage: begin
32084: 2010-03-23 14:21:56.310 [CBS] CreateSessionAndPackage: done
32084: 2010-03-23 14:21:56.310 [CBS] ...parents that will be auto-installed: 'WindowsServerBackup MicrosoftWindowsPowerShell '
32084: 2010-03-23 14:21:56.310 [CBS] ...default children to turn-off: '<none>'
32084: 2010-03-23 14:21:56.794 [CBS] ...current state of 'WindowsServerBackupCommandlet': p: Staged, a: Staged, s: UninstallRequested
32084: 2010-03-23 14:21:56.794 [CBS] ...setting state of 'WindowsServerBackupCommandlet' to 'InstallRequested'
32084: 2010-03-23 14:21:56.934 [CBS] ...current state of 'WindowsServerBackup': p: Installed, a: Installed, s: InstallRequested
32084: 2010-03-23 14:21:56.934 [CBS] ...skipping 'WindowsServerBackup' because it is already in the desired state.
32084: 2010-03-23 14:21:56.981 [CBS] ...current state of 'MicrosoftWindowsPowerShell': p: Installed, a: Installed, s: InstallRequested
32084: 2010-03-23 14:21:56.981 [CBS] ...skipping 'MicrosoftWindowsPowerShell' because it is already in the desired state.
32084: 2010-03-23 14:21:57.012 [CBS] ...'WindowsServerBackupCommandlet' : applicability: Applicable
32084: 2010-03-23 14:21:57.059 [CBS] ...'WindowsServerBackup' : applicability: Applicable
32084: 2010-03-23 14:21:57.106 [CBS] ...'MicrosoftWindowsPowerShell' : applicability: Applicable
32084: 2010-03-23 14:24:50.470 [CbsUIHandler] Initiate:
32084: 2010-03-23 14:24:58.676 [CbsUIHandler] Error: -2147010815 :
32084: 2010-03-23 14:24:58.676 [CbsUIHandler] Terminate:
32084: 2010-03-23 14:24:58.676 [CBS] Error (Id=0) Function: 'NativeMethods.GetPackageStatus(out status)' failed: 80073701 (-2147010815)
32084: 2010-03-23 14:24:58.676 [CBS] ...done installing 'WindowsServerBackupCommandlet '. Status: -2147010815 (80073701)
32084: 2010-03-23 14:24:58.738 [Provider] Skipped configuration of 'CommandLineTools' because install operation failed.
32084: 2010-03-23 14:24:58.738 [Provider]
[STAT] ---- CBS Session Consolidation -----
[STAT] For
'CommandLineTools'[STAT] installation(s) took '186.8790195' second(s) total.
[STAT] Configuration(s) took '0.0071557' second(s) total.
[STAT] Total time: '186.8861752' second(s).
32084: 2010-03-23 14:24:58.754 [Provider] Error (Id=0) Sync Result - Success: False, RebootRequired: False, Id: /RMTInstances/http___schemas.microsoft.com_sdm_Windows_ServerManager_WindowsServerBackup_2005_09_CommandLineToolsType_d9c54706-68ad-4445-bbd9-c5922ce4ade0.xml
32084: 2010-03-23 14:24:58.754 [Provider] Error (Id=0) Sync Message - OperationKind: Install, MessageType: Error, MessageCode: -2147010815, Message: Attempt to install Command-line Tools failed with error code 0x80073701., AdditionalMessage: The referenced assembly could not be found
32084: 2010-03-23 14:24:58.816 [ServerManagerCmd] Error (Id=0) Installation of [Windows Server Backup Features] Command-line Tools failed. Attempt to install Command-line Tools failed with error code 0x80073701. The referenced assembly could not be found
32084: 2010-03-23 14:24:59.331 [ServerManagerCmd] [STAT] Overall Sync Time: '187.8442394' second(s)
32084: 2010-03-23 14:24:59.346 [ServerManagerCmd] Error: Installation of one or more roles, role services, or features failed. Check the Server Manager log for additional information and try again.
