The git plugin is unable to clone the git repository. Attempts result in (full log attached):

$ git clone -o origin git@hostname:/home/git/repositories/project.git "e:\HUDSON_HOME\jobs\Project Trunk\workspace"
ERROR: Error cloning remote repo 'origin' : Could not clone git@hostname:/home/git/repositories/project.git
ERROR: Cause: Error performing git clone -o origin git@hostname:/home/git/repositories/project.git e:\HUDSON_HOME\jobs\Project Trunk\workspace
Trying next repository
ERROR: Could not clone from a repository
FATAL: Could not clone
hudson.plugins.git.GitException: Could not clone

I've confirmed that if Pageant is running and the appropriate key is added I can run the following command (from cmd.exe) without error:
git clone -o origin git@hostname:/home/git/repositories/project.git "e:\HUDSON_HOME\jobs\Project Trunk\workspace"

On a Windows machine, it appears that there are no provisions for specifying the SSH key so that this error can be avoided.