You might find that installing the latest update rollup 8 for Exchange 2007 SP1 server takes a long time to complete. The process seems to be stuck with the message “Creating native images for .NET assemblies”. It does complete the installation finally, but will take too much time.
This normally happens when you try to run the update on an exchange server in a test environment with no connection to the internet. As part of the installation, the server tries to lookup the certificate revocation list for each assembly it compiles in http://crl.microsoft.com and as there is no internet connection, it has to time out before proceeding to the next step.
Microsoft has an article with a fix here
An easier solution that has worked for me is to edit the hosts file and point crl.microsoft.com to 127.0.0.1 before installing the update rollup.