ok so ihad this problem like u guys from the last two patchs
what I did to fix this is the following
1- Changed my Windows XP style to Windows Classic [ It makes ur CPU run faster.]
2- Downloaded Tuneup utilities and scanned my pc, fixed error on drivers/cleaned registry/disk space. etc.
3- scanned my comp with AVG/spyware doctor
4- Allow Knightonline folder on all the anti virus/firewall/anti spyware etc.
5- Delete any other ko clients installed Even if it wasnt usko like japko or private servers
6- Delete all the stuff u dont need I had like 60 items on desktop I removed them all..
7- Set ur ko version to 1731 and download to 1739 then restart ur pc and run the game it shud run perfectly

Hope it works for you guys