So try downloading a newer forge... And can you tell me what version of python you have (python --version)?
I have been using forges latest's sucessful build, hot off the jenkins build system.
I am using python 2.7.3
Ah. that forge build is for 1.4.1pre. If deving on 1.3.2, you need build 318: http://jenkins.minecraftforge.net/job/forge/318/