I am seeing this on 4.6.14 . This is due to modsec thinking it is a SQL attack. I saw a popup indicating datatables saw an error and to look here:https://datatables.net/manual/tech-notes/7
Console showed these errors:
Failed to load resource: the server responded with a status of 403 (Forbidden)
https://www.xxxxxx.com/civicrm/ajax/contactrelationships?context=past&cid=10…_9=false&mDataProp_10=10&bSortable_10=false&iSortingCols=0&_=1462288897639 Failed to load resource: the server responded with a status of 403 (Forbidden)
When I disabled the modsec rule it worked without error. here is the rule:
SecRule ARGS|ARGS_NAMES|REQUEST_COOKIES|REQUEST_COOKIES_NAMES|XML:/|!ARGS:/body/|!ARGS:/content/|!ARGS:/description/|!ARGS:/message/|!ARGS:Post|!ARGS:desc|!ARGS:text|!ARGS:text_message|!REQUEST_COOKIES:/__utm/|!REQUEST_COOKIES:/_pk_ref/|!ARGS:sql_query "@rx [[]\"',().]{10}$|(?:union\s+all\s+select\s+(?:(?:null|\d+),?)+|order\s+by\s+\d{1,4}|(?:and|or)\s+\d{4}=\d{4}|waitfor\s+delay\s+'\d+:\d+:\d+'|(?:select|and|or)\s+(?:(?:pg_)?sleep(\d+)|\d+\s=\s*(?:dbms_pipe.receive_message((?:chr(\d+)(?:\s*\|\|\s*)?),\d+)|(select\s+\d+\s+from\s+pg_sleep(\d+)))))(?:\s(?:and|or)\s+(?(?:(\d{4})=\1|'(\w{4})'='\2|'%'=')|--\s*\w*|#)$|(select\s*(case\s+when\s*(\d+\s*=\s*\d+)\s+then\s+\d+\s+else\s+(?:0x[\0-9a-h]+|\d+)\s+end))|(?:(?:and|or)\s+(?'?(?:\w{1,4}|%)'?)?(?:=|<|>)(?'?\w{0,4}'?)?|order\s+by\s+\d+)(?:#|--\s*\w{0,4})?$" \
"id:1,rev:5,msg:'COMODO WAF: SQLmap attack detected',phase:2,severity:2,capture,block,setvar:'tx.sqli_points=+%{tx.points_limit4}',setvar:'tx.points=+%{tx.points_limit4}',logdata:'Matched Data: %{TX.0} found within %{MATCHED_VAR_NAME}: %{MATCHED_VAR}',ctl:'auditLogParts=+E',t:'none',t:'urlDecodeUni',t:'lowercase'"