Can you give more info about it?
How I must install driver?
What version of Kerio has conflict with WinPKFilter?
Actually the only requirement for WinpkFilter driver is starting between NDIS.SYS and TCPIP.SYS, but some hooking drivers(like the case with Kerio) may add additional conditions (like start before or after these drivers). In case with Kerio the conflict was detected when WinpkFilter driver strats before Kerio driver, but the problem gone if WinpkFilter starts after Kerio. Thats why we had changed load order to “Streams Drivers” Start:1. However, the situation may change from release to release (by the date of the post mentioned the problem was with the newest Kerio release, and there were no problems with previous releases).