If a service doesn't start within a set amount of time, Windows will kill it and put an error in the System event log. You might decide that you need to extend the service startup timeout. Or, if your services are complaining about a startup timeout too quickly, you might decide you need to check the startup timeout and fix it back to at least the default 60 seconds.

This beahviour has been observed in heavily loaded PVS environments while simultaneously booting hundreds of  PVS target devices from a single PVS server. Several targets may not fully boot to login screen, or may allow login but many services are not started, requiring a reboot to correct.

http://support.microsoft.com/kb/884495

To increase the service startup time yourself, create the following registry entry:
Subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control

Name: ServicesPipeTimeout
Type: REG_DWORD
Data: The number of milliseconds that you want to give the services to start in.

To create this registry entry, follow these steps:

1. Click Start, click Run, type regedit, and then click OK.

2. Locate and then click the following registry subkey:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control

3. Right-click Control, point to New, and then click DWORD Value.

4. In the New Value #1 box, type ServicesPipeTimeout, and then press ENTER.

5. Right-click ServicesPipeTimeout, and then click Modify.

6. Click Decimal, type the number of milliseconds that you want to wait until the service times out, and then click OK.
   For example, to wait 60 seconds before the service times out, type 60000.

7. Quit Registry Editor, and then restart the computer.