It looks like that error message comes from https://github.com/Cisco-Talos/clamav-devel/blob/dev/0.102/clamdscan/proto.c#L112, and is generated when a call to getaddrinfo (a C standard library function) fails.  The values passed to this call are directly based on what's in the clamd config file, so as Ged Haywood suggested, it'd be helpful to see what your config looks like so that we can diagnose further.  Specifically, this code deals with the LocalSocket, TCPSocket, and TCPAddr configuration options.