I could not reproduce the problem here. I had a look at the code, it uses SendMessageTimeout to send a HWND_BROADCAST with a timeout of 5 seconds.
The information box you are seeing comes from the -le option (log all exceptions) - that actually showed that we have some missing resources (which caused the exceptions) - whch made me realise those resources shouldn’t even be loading at all when running fbcmd - I just checked in a fix for that (improves fbcmd startup time a bit).
have a look in %TEMP% there should be an exceptions.txt - send that to support @ finalbuilder.com and I’ll take a look.