Many people have reported that after updating to OS X 10.7.4, they are finding a ton of smcReaKeyAction entries being written to their system.log files. This appears to be caused by Apple updating the SMC kernel extension, which is conflicting with some third-party system monitoring software such as iStat, Temperature Monitor, and SMCFanControl. If you are experiencing this issue, make sure your third-party monitoring software is up to date, or disable things until updates becomes available to resolve this issue.