A common problem after setting up SharePoint 2010 is to get the System.Security.Cryptography.CryptographicException – Keyset Not set error.
A few notes regarding this:
This is a known issue with .NET and SP2010.
It is not a critical issue however.
The Timer service is recycled every so often to reclaim system resources. The exception is thrown during the shutdown process. When you check the timer service everything seems to running fine, except that you see the exception logged in the event log of course.
If you have Visual Studio installed, you may also see the “do you want to debug” dialog.
A detailed explanation of why this happens is provided here and here
Although the author above mentions why this problem occurs, there is no real “solution” to the issue which is a bit troublesome.