You have a .NET Framework 2.0-based Multi-AppDomain application that uses objects. These objects have finalizers that start ThreadPool methods, for example, sockets. When you run the application, you notice that the CPU usage increases significantly.
This problem occurs because the finalizer invokes a ThreadPool method when an application domain is unloaded. Then, the data in the thread pool is corrupted and stops working for any other application domain.
Hotfix Replacement Information
The hotfix that corresponds to KB971988 has been superseded with the hotfix KB981574, which contains all fixes that were previously included in KB971988. You should use the hotfix KB981574 to fix the issues described in KB971988. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
981574 The splash screen stays open longer than usual when you try to start Excel on a computer that has the .NET Framework 3.5 SP1 installed
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.