When attempting to install/update HWSensors and HWMonitor, the installer goes through the motions visually, but does not actually install HWMonitor.app. Issue exists when attempting to use the built in updater -> installer or directly launching the installer package.
User has to manually extract HWMonitor.app from the package using Pacifist, even if previous HWMonitor is deleted from /Applications first.
HWSensors installer can find and update app anywhere on the disk, preferably last used one. This installer feature was implemented by users request in case that app was relocated to Utilities folder etc. Try to search and delete HWMonitor app duplicates.
That may be exactly what happened. I had some older unzipped folders from before I started using the installer packages. Hopefully knowing this I'll not have the issue anymore. :)