I've been in touch with Tom Igoe who wrote the original X10 receive code. He has now modified it to work with 1.0.1 (arduino.h and wire library mods), it compiles but unfortunately it doesn't work for me. I live in the UK (50Hz) and he is in 60Hz land and doesn't have any X10 kit to test it with - can anyone help?
The new code is at https://github.com/tigoe/x10
Meanwhile I'm trying other routes.
X10ex from http://load-8-1.blogspot.com/2010_06_01_archive.html
also works OK with 0.22 but fails with 1.0.1. It looks like a timing issue as the commands are received by the arduino, indicating the interrupt is OK but they are being interpreted with the wrong house code and value. I've emailed the author and am waiting a reply.