My story: after updating from version 1.0.5 to 1.0.6, the program wouldn't start anymore. That is, when I open it the exe file, it loads the program and then immediately closes, without showing the program's window even for a moment. In the processes list I could see that the program was indeed loaded for a moment, but then it immediately closed.
My solution: I tried a more thorough uninstallation using "Revo Uninstaller Pro 3.1.4", and when I reinstalled Wifi Guard afterwards, it worked. In case it is of any help, below are a few leftover registry values which the default uninstaller did not remove (I'm running Windows 7 64-bit).
Alternatively, simply use the portable version - it works just fine (both 32-bit and 64-bit) without any need of ever install or unuinstall anything.