git-upload-pack died of signal 13

Dear List,

we got "git-upload pack died of signal 13" error when pushing using this 
command:

  Executing: "/usr/lib/git-core/git-http-backend" env: 
"CONTENT_TYPE=application/x-git-upload-pack-request" 
"GIT_HTTP_EXPORT_ALL=true" "SERVER_PORT=443" 
"CODEBEAMER_SMART_SCM_SERVLET=true" "REMOTE_ADDR=91.82.170.74" 
"REMOTE_HOST=91.82.170.74" "SERVER_SOFTWARE=Apache Tomcat/6.0.35" 
"SERVER_NAME=codebeamer.com" 
"GIT_PROJECT_ROOT=/home/akos/repository/git" "REMOTE_USER=zl" 
"PATH_INFO=/cbdev-git/git-upload-pack" "QUERY_STRING=" "AUTH_TYPE=Basic" 
"GATEWAY_INTERFACE=CGI/1.1" "SERVER_PROTOCOL=HTTP/1.1" 
"REQUEST_METHOD=POST" "CONTENT_LENGTH=1157" 
"REQUEST_URI=/app/git/my-git/git-upload-pack"

What may be the cause?

Thanks in advance,
Ákos Tajti