Exchange Server setup encountered an error during Exchange 2007 SP2 install

When I try to install service pack 2 on my Exchange 2007 SP1 server, it fails with this message: "Exchange Server setup encountered an error".  I've installed SP2 successfully on 5 other servers, this is the first one with a problem. This server is running Windows Server 2008 Enterprise, the other 5 are running Windows Server 2003. I have installed the Windows Installer 4.5 and restarted.  The Exchangesetuplog file just shows the information below, and the application log does not have any errors.  I'm using the same account I used on the other servers.   

[11/3/2009 5:50:46 AM] [0] Starting Microsoft Exchange 2007 Setup
[11/3/2009 5:50:46 AM] [0] **********************************************
[11/3/2009 5:50:46 AM] [0] Operating System version: Microsoft Windows NT 6.0.6001 Service Pack 1.
[11/3/2009 5:50:46 AM] [0] Setup version: 8.2.176.2.
[11/3/2009 5:50:46 AM] [0] Logged on user: AMS\++++.
[11/3/2009 5:50:47 AM] [0] Command Line Parameter Name='mode', Value='Upgrade'.
[11/3/2009 5:50:47 AM] [0] Command Line Parameter Name='sourcedir', Value='T:\temp\exchsp2'.
[11/3/2009 5:50:47 AM] [0] Command Line Parameter Name='fromsetup', Value=''.
[11/3/2009 5:50:47 AM] [0] ExSetupUI was started with the following command: '-mode:upgrade -sourcedir:T:\temp\exchsp2 /FromSetup'.