Running CiviCRM 1.9.11960 on a relatively new mediatemple dedicated virtual server and ran into this error when clicking the "Backup Data" option in Admin:
malformed header from script. Bad header=Content-Type Extension='.gz' C: index.php, referer: http://DOMAINOMITTED/civicrm/admin?reset=1
I removed this line in CRM/Core/BAO/DomainDump.php:
header("ContentType Extension='$ext' ContentType='$type'");
And replaced it with:
Which seems to work fine. Dunno if there is some difference in Apache versions in play or not.