Uhhhhh... not so fast.
If the 2nd leg (LAX-EWR) is the first segment of the LAX-RIO ticket, and the 5th leg (LAX-EWR) is the return of the EWR-LAX ticket, then what you have is specifically a "back-to-back", since you are returning to the origin on a different ticket from the one you started on.
While I think the risk of having a problem is small, there is a risk.
[This message has been edited by RichG (edited 01-07-2001).]