Win7 after reboot, no icons, explorer.exe at 100% CPU

On a Windows 7 x64 system with dual monitors, after rebooting the Fences background rectangles and title bars are displayed but no icons appear.  The Desktop is unresponsive to mouse clicks because the Explorer.exe process is consuming 100% of a CPU core (25% overall on a four-core PC.)  I can leave it running for a half hour or longer and the situation doesn't change.  Killing the Explorer.exe process and restarting it manually from Task Manager displays the icons (though now the Fences backgrounds and titles are gone) but the computer remains unresponsive to mouse clicks and Explorer.exe goes back to full CPU consumption.  Disabling Fences allows the Desktop icons to start responding again but re-enabling takes it back to the unresponsive hung-Explorer state.  Tried uninstalling and reinstalling Fences and it behaves the same way afterward.  We have Fences running just fine on two other PC's which are both single monitor Win7 x64 machines, so I'm not sure if the dual monitors are triggering the problem or if there's something else about this particular machine which leads to this behavior.