A sudden lack of permission

  Dear All

I have been using git quite happily for a good while, pushing to my remote. Suddenly this afternoon the remote told me I didn't have permission:

     $ git push
     ivan@remote.org's password:
     Counting objects: 19, done.
     Delta compression using up to 2 threads.
     Compressing objects: 100% (11/11), done.
     Writing objects: 100% (11/11), 1.04 KiB, done.
     Total 11 (delta 8), reused 0 (delta 0)
     error: insufficient permission for adding an object to repository 
database ./objects

     fatal: failed to write object
     error: unpack failed: unpack-objects abnormal exit
     To ivan@remote.org:/var/www/git/my_repos.git
      ! [remote rejected] master -> master (n/a (unpacker error))
     error: failed to push some refs to 
'ivan@remote.org:/var/www/git/my_repos.git'

I had sufficient permission even this morning!

Please could someone tell me what might have happened and, more importantly, how I can start pushing to the remote again? The project in my_repos is large, so I'd rather not start a new repos from scratch.

With thanks and best wishes

Ivan