Question : EX2k7SP1 Rollup #4: Ended Prematurely

I'm trying to install Exchange 2007 SP1 Rollup #4 onto an existing EX2k7 SP1 64-bit Enterprise installation.  I'm using Exchange2007-KB952580-v2-x64-EN.msp.

When I run the .MSP, it spends a good while "computing space requirements," before prompting me to begin the install and accept the license terms.  Then the "Installing..." window gets busy for about 10 minutes.

Unfortunately, the end result is a blue, white and gray dialog - a normal .MSP screen - which says...

"Setup Wizard for Update Rollup 4 for Exchange Server 2007 Service Pack 1 (KB952580) ended prematurely because of an error.  Your system has not been modified.  To install this program at a later time, please run the installation again."

To my eyes, there's nothing conclusive in the logs which are dumped into C:\ExchangeSetupLogs .

Curiously, Rollup 4 appears in Add/Remove programs and can be removed without incident.

Looking for advice and sympathy :)  Thank you.

Answer : EX2k7SP1 Rollup #4: Ended Prematurely

Haha!  Made it go.  Finally.
.NET Runtime Optimization Service v2.0.50727_X86
.NET Runtime Optimization Service v2.0.50727_X64
For as long as I can remember, I've disabled these services.  If I want the optimizer to kick off I'll manually enable the service.
This morning, on a hunch, I set the services to manual and started them.  RU5 completed sucessfully.