Kernel SMC::smcReadKeyAction error
Are you on OS X 10.7.4 ?
Then an explanation and possible solution might be found here on CNet:   

Tackling SMC console errors after OS X 10.7.4 update

"Might", because it didn't work for me - even after uninstalling iStat Menus v2.x, so it must be some other application(s) on my part that is causing this...