with the release of Exchange 2007 Rollup 5, a problem surfaced that is Exchange 2007 managed services did not start automatically after Rollup application, however they would start manually. In most of these cases the computer in question was not connected to the Internet. Investigation showed that the problem was the timing of the Windows Service Control Manager (SCM) and validation of all of the certificates associated with a service within the SCM timeout. In the case of computers that were connected to the Internet, the problem seemed to be network latency, as the problem in those cases can happen only intermittently.
Why this happens? To sum it up: the problem did not manifest itself until Exchange 2007 managed binaries were signed with two certificates (because the original one was expiring). For Exchange 2007 RTM this occurred when RU5 was released. Because now .Net Framework Common Language Runtime (CLR) attempted to validate two certificates by connecting to http://crl.microsoft.com, the process took longer, to the point where SCM timeout would pass and services would fail to start up automatically. In environments with limited or no Internet connectivity, this might fail every time. In other cases, this might fail intermittently based on current network state and load.