First of all,
Start all again as a simple user:
1)be sure to have a user account on all remote boxes you want to login...
2)create a .rhosts file with 640 permission and in it put the name of allowed servers followed by your account name
start simple : 1 remote access => 2 files one on each box in the $HOME directory (nowhere else!) eg in box1 file you should have one line: box2 myname and in box2 box1 myname
3) try:
Does it work? from box1: remsh or rsh box2

4) if it doesnt work there is no point complicating things:
Solve your issue first:
a) if its not working it may be name resolution does box2 know of box1?
b) Are the boxes up with more than one lan card?
c) etc...

One you get your account working you can figure out what you will have to do to get your su to work...

Good luck