Symptoms
When you launch an Office 2010 application (such as Excel 2010 or Word 2010), you may be prompted for credentials for a proxy server - office14client.microsoft.com - as shown in this image:
Cause
This is a known issue with the update described in Knowledge Base article 2956191.
Resolution
To resolve this issue, please install the update found here: http://www.microsoft.com/en-us/search/result.aspx?q=KB3054875&form=DLC
