I'm having the same problem as BostonDriver -- as per niemiro's response, here's the log file I found at: C:\Windows\Logs\CBS (is this the right file?)
2011-03-26 15:00:05, Info CBS Starting TrustedInstaller initialization.
2011-03-26 15:00:05, Info CBS Loaded Servicing Stack v6.1.7601.17514 with Core: C:\Windows\winsxs\amd64_microsoft-windows-servicingstack_31bf3856ad364e35_6.1.7601.17514_none_678566b7ddea04a5\cbscore.dll
2011-03-26 15:00:06, Info CSI 00000001@2011/3/26:22:00:06.587 WcpInitialize (wcp.dll version 0.0.0.6) called (stack @0x7fee992e94d @0x7fee9be9839 @0x7fee9bb34d3 @0xff0ce94c @0xff0cd769 @0xff0cdaff)
2011-03-26 15:00:06, Info CSI 00000002@2011/3/26:22:00:06.680 WcpInitialize (wcp.dll version 0.0.0.6) called (stack @0x7fee992e94d @0x7fee9c36806 @0x7fee9c02a9c @0x7fee9bb35a9 @0xff0ce94c @0xff0cd769)
2011-03-26 15:00:06, Info CSI 00000003@2011/3/26:22:00:06.680 WcpInitialize (wcp.dll version 0.0.0.6) called (stack @0x7fee992e94d @0x7fef0fe8728 @0x7fef0fe8856 @0xff0ce444 @0xff0cd7ae @0xff0cdaff)
2011-03-26 15:00:06, Info CBS Ending TrustedInstaller initialization.
2011-03-26 15:00:06, Info CBS Starting the TrustedInstaller main loop.
2011-03-26 15:00:06, Info CBS TrustedInstaller service starts successfully.
2011-03-26 15:00:06, Info CBS SQM: Initializing online with Windows opt-in: False
2011-03-26 15:00:06, Info CBS SQM: Cleaning up report files older than 10 days.
2011-03-26 15:00:06, Info CBS SQM: Requesting upload of all unsent reports.
2011-03-26 15:00:06, Info CBS SQM: Failed to start upload with file pattern: C:\Windows\servicing\sqm\*_std.sqm, flags: 0x2 [HRESULT = 0x80004005 - E_FAIL]
2011-03-26 15:00:06, Info CBS SQM: Failed to start standard sample upload. [HRESULT = 0x80004005 - E_FAIL]
2011-03-26 15:00:06, Info CBS SQM: Queued 0 file(s) for upload with pattern: C:\Windows\servicing\sqm\*_all.sqm, flags: 0x6
2011-03-26 15:00:06, Info CBS SQM: Warning: Failed to upload all unsent reports. [HRESULT = 0x80004005 - E_FAIL]
2011-03-26 15:00:06, Info CBS No startup processing required, TrustedInstaller service was not set as autostart, or else a reboot is still pending.
2011-03-26 15:00:06, Info CBS NonStart: Checking to ensure startup processing was not required.
2011-03-26 15:00:06, Info CSI 00000004 IAdvancedInstallerAwareStore_ResolvePendingTransactions (call 1) (flags = 00000004, progress = NULL, phase = 0, pdwDisposition = @0x191f870
2011-03-26 15:00:06, Info CSI 00000005 Creating NT transaction (seq 1), objectname [6]"(null)"
2011-03-26 15:00:06, Info CSI 00000006 Created NT transaction (seq 1) result 0x00000000, handle @0x1f0
2011-03-26 15:00:06, Info CSI 00000007@2011/3/26:22:00:06.883 CSI perf trace:
CSIPERF:TXCOMMIT;104591
2011-03-26 15:00:06, Info CBS NonStart: Success, startup processing not required as expected.
2011-03-26 15:00:06, Info CBS Startup processing thread terminated normally
2011-03-26 15:00:06, Info CSI 00000008 CSI Store 1774864 (0x00000000001b1510) initialized
2011-03-26 15:00:06, Info CBS Session: 30141441_719678931 initialized by client WindowsUpdateAgent.
2011-03-26 15:00:11, Info CBS Archived backup log: C:\Windows\Logs\CBS\CbsPersist_20110326220005.cab.
Thanks for any help!