Can you post your curl request?
This works for me:
curl -k -u admin:changeme -d 'search="search * | head 10"' -d "output_mode=csv" https://localhost:8089/servicesNS/admin/search/search/jobs/export
"_serial","_time",source,sourcetype,host,index,"splunk_server","_raw"
0,"2013-04-30 19:59:04.105 BST","/opt/apache/log/sl_access_combined.log","sl_access_combined","example.splunk.com","example","splunk.example.com","1.2.3.4 - - [30/Apr/2013 18:59:04:105] ""POST /url HTTP 1.1"" 503 878 ""http://example.com/referer"" ""Googlebot/2.1 ( http://www.googlebot.com/bot.html) "" 623"
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