This bug is fixed in 1.9.2 (latest version as of now). Download here.
ORIGINAL ANSWER
This is a reported bug, with a fix already - not sure when it will be released as a windows install yet.
To fix this problem in git 1.9.0 you must uninstall/reinstall. On reinstalling select the following options.
[x] Windows Explorer integration
(*) Simple context menu (Registry based)
[x] Git Bash Here
[x] Git GUI Here
( ) Advanced context menu (git-cheetah plug-in)
This way, the bug with the git-cheetah plugin will longer present itself.