Since I had problems with this script, http://wiki.mikrotik.com/wiki/Dynamic_DNS_Update_Script_for_No-IP_DNS for update IP address to No-IP DNS server I rewrite it to make compatible for RouterOS version 6.7.
The problem with that script is the function :toarray, Code: :set noiphostarray [:toarray $noiphost]
That line produces a malfunction of the script because it never saves the value of the current IP address in var $previousIP, so the script is constantly updating the IP address when it is not necessary because it hasn't changed.
Here is my debugged script working on RouterOS version 6.7: