If you are running a volume licensed edition of Office 2010 and it needs to be activated, you may see this message when you open any Office 2010 application:
This message means Office is failing to activate against a KMS host on your network. KMS activation is the default activation type when you install a volume license edition of Office 2010. There are two ways of getting Office 2010 activated:
- Enter a MAK key and activate over the internet or phone
- Setup an Office 2010 KMS host and activate using it.
Option 1: Enter a MAK key and activate over the internet or phone
To enter a MAK key, click the “Change Product "Key” button and enter your key when prompted: 
Click “Continue”, then “Install Now”.
Office will configure itself. Close any open Office 2010 applications. The next time you launch an Office application you will see a screen like this:
Go through the activation wizard. Once it is done you will be activated and should not see any of these messages again.
Option 2: Setup an Office 2010 KMS host and activate using it.
See this blog post for a very detailed guide on how to setup an Office 2010 KMS Host: http://blogs.technet.com/b/odsupport/archive/2010/06/01/office-2010-kms-installation-and-troubleshooting.aspx