Sign in with Microsoft
Sign in or create an account.
Select a different account.
You have multiple accounts
Choose the account you want to sign in with.


On a computer that is running the Microsoft Office Communications Server 2007 R2 Group Chat client, you try to log off or try to shut down the computer. In this situation, the Group Chat client crashes. Additionally, you receive the following error message:

System.NullReferenceException: Object reference not set to an instance of an object.


To fix this problem, install the following cumulative update:

2491979 Description of the update for Office Communications Server 2007 R2 Group Chat client: March, 2011


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

Need more help?

Want more options?

Explore subscription benefits, browse training courses, learn how to secure your device, and more.

Communities help you ask and answer questions, give feedback, and hear from experts with rich knowledge.

Was this information helpful?

What affected your experience?
By pressing submit, your feedback will be used to improve Microsoft products and services. Your IT admin will be able to collect this data. Privacy Statement.

Thank you for your feedback!