I try it and can't solve current solution. It solved when i just visit to my GitLab unicorn log that displays the problem:
I, [2014-02-10T17:46:29.953026 #5799]  INFO -- : worker=0 ready
E, [2014-02-10T17:47:52.026874 #5719] ERROR -- : worker=1 PID:5728 timeout (181s > 180s), killing
E, [2014-02-10T17:47:52.039670 #5719] ERROR -- : reaped #<Process::Status: pid 5728 SIGKILL (signal 9)> worker=1
the worker timeout says about problems with long time running for git clone.
It fixed in GitLab Unicorn config.. just change 180 seconds to bigger in config/unicorn.rb
timeout 360
If you use other web server or use proxy Nginx, possible you need also:
  server {
       ...
    # if a file, which is not found in the root folder is requested,
    # then the proxy pass the request to the upsteam (gitlab unicorn)
    location @gitlab {
      proxy_read_timeout 600; # https://github.com/gitlabhq/gitlabhq/issues/694
      proxy_connect_timeout 600; # https://github.com/gitlabhq/gitlabhq/issues/694
      proxy_redirect     off;
      proxy_set_header   X-Forwarded-Proto $scheme;
      proxy_set_header   Host              $http_host;
      proxy_set_header   X-Real-IP         $remote_addr;
      proxy_pass http://gitlab;
    }
  }
pay attention to part of proxy_read_timeout and proxy_connect_timeout.