I've run Kerio for 3 years, but have network / Internet share managed via a router. I take it you are using ICS, sharing Internet through your computer with other attach computers within your network.
The following are options / view I have when running via router. Do not know how interchangeable they are when interfacing with ICS ...
Network / Applications Tab ... Enable Network Security Module is "Ticked".
Network / Trusted Area Tab ... "Address / Dialup number Header column"
Using the "Add" feature, try adding the address of all other computers in your network.
PLEASE understand, this is only a suggestion .. Like I said my configuration is via a router. Above suggestions may / may not work.

SOME OF THESE OPTIONS / CHANGES may require a rebooting host and networked computers.