Recently I've seen severe load spikes (up to 8-9) when using mc to copy large files to a directory mounted via CIFS.  At first I thought the system had hung, as it became very unresponsive (pointer not responding to mouse movements, keystrokes having no effect etc.).  However, I was eventually able to ssh in from another machine and in time the load levelled off.  This pattern kept on repeating, until I stopped the copying job in mc.

This is with a Fedora Core 3 system running kernel 2.6.12-1.1381smp - it's a dual Athlon with 2G RAM and an e1000 NIC.  The directory it is mounting resides on a Buffalo TeraStation.