UPDATE 4/20/2011: We have now identified the problem and have a solution for customers that were impacted by it
Please see the following KB article for the resolution of this problem:
We have become aware of a problem that impacts Exchange management tools on servers running Exchange 2010 on Windows Server 2008 SP2.
Note: Windows 2008 R2 SP1 systems do not seem to be impacted. Windows 2008 R2 RTM is impacted.
The symptoms of the problem are:
The following events could be logged in the Application event log:
While we are still investigating this problem, the failures seem to start after the .NET security update KB 2449742 (MS11-028) is installed. The only workaround that we have identified up to now is a removal of this security update.
Warning: We do not recommend that you uninstall any security updates, but we are providing this information so that you can implement this procedure at your own discretion. Use this procedure at your own risk. Removing a security update could may make a computer or a network more vulnerable to attack by malicious users or by malicious software such as viruses.
We will update this blog post with more information as it becomes available.