Occasionally, a computer account can lose its secure channel to a domain controller.
How can secure channel be reset without rebooting the computer?
The computer in question is a clustered SQL Server running Server 2008 R2 in a 2008 R2 Functional Level Active Directory domain and forest.
nltest.exe can be used to check the channel and attempt to reset it.
If that does not do it, you can restart the netlogon service (I mainly use PowerShell, so I'll give an example of that).
I ran the nltest command after restarting the service to validate that the secure channel was back in operation.
If you've made some network changes (IP Addresses, changing hardware, virtualizing, etc..) you might want to flush your dns cache and clear your arp table before running the above commands.
I've had some instances where a machine will decide to use an off-site domain controller (elsewhere on our WAN) as it's logon server and map offsite network drives instead of local ones; that can be resolved by resetting the secure channel directly:
UPDATED for new versions of powershell
Open PowerShell AsAdministrator
If False then run:
If repaired you will see message, if it fails then try adding a credential