radiation myelopathy

I have colon cancer. Had radiation and chemo therapy in Sept/Oct 2006 and surgery in Dec. Was doing fine post-surgery until about the end of January. Then I noticed that my legs were getting weaker, my feet were cold and I was stumbling when I walked. It got progressively worse where my left leg was almost completely numb from the knee down. My right leg had most of the same symptoms but not as bad. My docs can't tell me what's causing this. There's some thinking that it might be radiation induced transient myelopathy, but my docs disagree on this diagnosis. Has anybody experienced the same kind of problem?