Git push error '[remote rejected] master -> master (branch is currently checked out)'

Yesterday, I posted a question on how to clone a Git repository from one of my machines to another, How can I 'git clone' from another machine?.

I am now able to successfully clone a Git repository from my source (192.168.1.2) to my destination (192.168.1.1).

But when I did an edit to a file, a git commit -a -m "test" and a git push, I get this error on my destination (192.168.1.1):

git push                                                
hap@192.168.1.2's password: 
Counting objects: 21, done.
Compressing objects: 100% (11/11), done.
Writing objects: 100% (11/11), 1010 bytes, done.
Total 11 (delta 9), reused 0 (delta 0)
error: refusing to update checked out branch: refs/heads/master
error: By default, updating the current branch in a non-bare repository
error: is denied, because it will make the index and work tree inconsistent
error: with what you pushed, and will require 'git reset --hard' to match
error: the work tree to HEAD.
error: 
error: You can set 'receive.denyCurrentBranch' configuration variable to
error: 'ignore' or 'warn' in the remote repository to allow pushing into
error: its current branch; however, this is not recommended unless you
error: arranged to update its work tree to match what you pushed in some
error: other way.
error: 
error: To squelch this message and still keep the default behaviour, set
error: 'receive.denyCurrentBranch' configuration variable to 'refuse'.
To git+ssh://hap@192.168.1.2/media/LINUXDATA/working
! [remote rejected] master -> master (branch is currently checked out)
error: failed to push some refs to 'git+ssh://hap@192.168.1.2/media/LINUXDATA/working'

I'm using two different versions of Git (1.7 on the remote and 1.5 on the local machine). Is that a possible reason?