Ditto, but it could also mean that somebody stuck straight tap water in the radiator in place of glycol...in which case the orange junk is the rust from the water jacket.

Ok, flush it clean and look for leaks. What does the radiator core look like (take a peek down the radiator cap hole and look at the ends of the core..you are looking for a bunch of that orange crud plugging up the end of the cores.)

On curt'* note, while looking at the radiator, get the car back up to full operating temperature with a 70/30 mix of green coolant and gently slide your hand from the top to the bottom of the radiator over the fins. Hot areas are where the coolant is flowing and cold areas are where its clogged. This will be a good indication of whether or not its the radiator giving you the cooling issue.

Something is definitely wrong for you to be getting that hot on the freeway especially since thats when air is being rammed through the fins, that is usually the time when the cooling fan becomes absolutely useless.

Personally, I think its the radiator, and replacing it would be your best bet.

Also, I do believe you can add 1 or 2 bottles of prestone super radiator flush to the premixed coolant, and drive it like that for a bit and allow it to break down more sediment, then waterflush it about 4-5 times.

You may also want to back flush the radiator after driving with the superflush by removing both radiator hoses, radiator cap on, and running as much water possible through the bottom outlet. I once had a spare radiator hose, a pvc reducer and a spare length of garden hose setup together so the hose would screw onto the end of the normally used hose or sprayer nozzle, and the other end would clamp onto the radiator. Worked especially well when the radiator was removed and was set on its side, inlet down, gravity on the assist for removing built up sediment. It actually worked quite well for me.