I'm seeing a similar issue with Windows 8. I had PC Monitor running perfectly with Windows 7 including wake on LAN (from both internet and local network) - however since changing to Windows 8 I'm seeing some strange issues.
Basically, if I "shut down" the PC via the PC Monitor app, wake on LAN works as expected.
However, if I shut the computer down via the charm menu, wake on LAN does not work. Even stranger is that when I do this, the stats in the PC Monitor app appear not to update, so when the machine is powered back on, PC Monitor will show that the machine has been online the whole time when it has not.
Is there some strange compatibility issue with Windows 8, or is this due to my computer configuration? At the moment I've taken to shutting down the PC via the PC Monitor app rather than the charm menu but this really shouldn't be necessary.
Any help would be greatly appreciated. Cheers!