i dont no what O/S your using.. but ya
nah it really doesnt matter mr. dreamscape. try it

i have on 8 different boxes. with and without routers, on my pc, on dedi hosts, on others pc's, though I always use windows 2003 server. im not sure what your exactly doing, but this is something hardcoded built into the software, not hardware. there are hundreds of computer programs that use this loopback function to communicate to itself on another port or on another program, they would all fail.. if this was the case of a 'faulty' router. it was probably something else you were doing incorrectly

you must understand what loopback function itself is... its a 'superficial' IP address to communicate to itself (meaning its not real), windows wouldnt allow such a thing to occur and send a loopback address to a router... as every computer has this IP, it would have no way to tell one from another.
quite possibly you might be using an ancient version of your O/S, or some very unusualy router.. i would guess anything made in the last 10 years would have enough sense for this to not occur.
i see you are certified computer guy
i think you might be mixing NAT loopback and internal loopback.. as they are different.
i wont argue though that NAT loopback has troubles with routers

and it causes problems.