If you run them in the same computer, then use 127.0.0.1 (really, use it, not the physical address). It is not really the same thing as the physical interface of your computer. Besides 127.0.0.1 works even without any NICs (network interface cards).
AFAIK LFS cannot operate insim on other than localhost (could be wrong but don't know how to change it then). In vcom there is still the same forced restriction, even you can give other than localhost address too. Currently it has been bit like a reminder for me to give user ability to change the interface (other than loopback). Quite simple really, but since it wasn't important for me I have posponed it (ok, i make it to the next ver). But honestly it is bit hard to think good reasons running them in different computers.
I got the idea you were running them in the same computer (address). Then you cannot use those 2 ports in manager either. If the source and destination addresses are the same (loopback) the port numbers use the same 'pool'. So both cannot be for example 29995. For example in manager i put "port = 29990" (instead of 29997) in the insim section and in vcom setup file system section i put "lfs_address=127.0.0.1:35000;". The addresses in manager and vcom are always 127.0.0.1. That works fine for me.
You could have been bit more specific in the first post. At least we could have saved the effort writing couple of posts and 1 day of time. For example I'm still not 100% sure if you run them in the same or different computers