Sounds like it has local echo on.
I normally use CRT (
free trial). Just now, I installed HyperTerminal to give it a try. HyperTerm doesn't work like that for me, but CRT does... when I tried just now with HT, it doesn't echo my text. Strange. prolly checking for a Carrier Detect or something.
Well, if you wanna download CRT and give it a try (it's really an excellent telnet program and just has serial as an extra)... it's not going to fix your problem, but it will help narrow down where the problem is. :/