git-push error: Cannot write keep file

Hello,
	I am having the following error when I try to git push.


rdarder@shiny:~/Sources/promotoras$ git push origin ranto:ranto
Counting objects: 256, done.
Compressing objects: 100% (199/199), done.
Writing objects: 100% (213/213), 216.94 KiB, done.
Total 213 (delta 60), reused 1 (delta 0)

fatal: cannot write keep file

error: unpack failed: index-pack abnormal exit
To ssh://fherrero@10.7.1.20:2222/var/www/promotoras.git
  ! [remote rejected] ranto -> ranto (n/a (unpacker error))
error: failed to push some refs to 
'ssh://fherrero@10.7.1.20:2222/var/www/promotoras.git'


I couldn't find any significant description on the error "cannot write 
keep file". git-fsck passes without errors in both repositories, and I 
find no permission problems. Can anyone give me some directions on how 
to diagnose this?

Regards,

Rafael