Windows Explorer will not open. Clicking on Computer in the start menu, clicking on a folder icon on the desktop, clicking on user name link on start menu all have the same result. Windows Explorer will not open. No error messages show. Programs with icons on the desktop will run.
Windows 7 64-bit SP1, Lenovo T530 laptop, Windows updates current.
The problem is intermittent. Restarting will often solve the problem temporarily. Starting in Safe Mode will solve the problem temporarily.
SFC /scannow has been run. All files present and current.
Virus and Malware scans done with multiple programs (Microsoft Security Essentials, Avast, McAfee Security Scan, Kaspersky rescue disk, Malwarebytes, Super-Anti Spyware).
I have not found an action that will precipitate the failure.