.gitignore vs untracked working file

Hi

I have a .gitignore rule to ignore everything in bin/ directories but I cannot change branch because of a file lying in a bin/ directory which actually should be ignored. What am I doing wrong?

$ git branch
  master
* mybranch

$ git status # On branch mybranch nothing to commit (working directory clean)

$ cat .gitignore *.class .cvsignore CVS/ .metadata/ build/ bin/ .#*

$ git checkout master error: Untracked working tree file 'Project/bin/path/file.jjt' would be overwritten by merge.

$ git --version git version 1.6.4.msysgit.0

thx

Bost