Git (SHA1) problem on Mac

Hi,

I've got a problem with Git on my Mac, and I've exhausted Google and #git (irc), perhaps somebody can help?

I'm using git version X installed from source, I'm on Mac OS X 10.4.11.

Here's the problem I'm seeing:

[imac:~]$   mkdir git-test
[imac:~]$   cd git-test
[imac:~/git-test]$   git init
Initialized empty Git repository in .git/
[imac:~/git-test]$   touch README
[imac:~/git-test]$   git add README
[imac:~/git-test]$   git commit -m 'first commit'
Created initial commit b6e6cb6: first commit
  0 files changed, 0 insertions(+), 0 deletions(-)
  create mode 100644 README
[imac:~/git-test]$   git remote add origin git@github.com:mkdynamic/ 
git-test.git
[imac:~/git-test]$   git push origin master
Counting objects: 3, done.
Writing objects: 100% (3/3), 215 bytes, done.
Total 3 (delta 0), reused 0 (delta 0)
fatal: final sha1 did not match
error: unpack failed: unpacker exited with error code
To git@github.com:mkdynamic/git-test.git
  ! [remote rejected] master -> master (n/a (unpacker error))
error: failed to push some refs to 'git@github.com:mkdynamic/git- 
test.git'

I can confirm that it is not an issue with the remote repo, as I similar 'final sha1 did not match' errors when i try to do local fetches.

Any clues/advice on what to do next?

Many thanks,

~ Mark