I have the same problem with "dhcp leases"
"arp" "firewall" and "address list" are adding without any problem (from Mikrotik API)
Configured using this wiki page: http://wiki.ubilling.net.ua/doku.php?id=mikrotikapi
Ubilling Version: 0.7.0 rev 4720 (installed using UBinstaller)
RouterOS: 6.32.1
P.S. you can answer me in russian
Thank you