If you save a flight plan (preferably without SID, STAR and TRANS), open it with the default FSX Flight Planner, then save it again. FSX Flight Planner will not rename the waypoints (even though they differ from the ones in FSX nav data base), nor their co-ordinates. Then load it with the 757 FMS and then add the SID, STAR and TRANS using the FMS/CDU. This always works for me.

As windycityflyer said, the way that FSC8 saves a flight plan is quite different to the way FSC9 does. A good reason to upgrade to version 9 is that you can add SID, STAR and TRANS to the flight plan. I rarely save the plan with those, but I use it to give me a beter idea of what SID, STAR and TRANS to use in the FMC of my modern airliners. I find that it is also easier than reviewing the flight plan on the HSI.

Mark