Thats pretty odd, maybe try delete the V8 folders first then install the latest version. I checked the log and it doesn't exactly say where the checksum failed but last thing it did before kicking you was check the car checksum. Can you try one of the other cars maybe its just the Holden your trying to join with. Also if you update any mods you need to restart the game for it to take effect but I assume you already did that.
Here is what the server says when you joined.
Code:
Bogor
REQUESTED CAR: supercars_holden*
CALLING PLUGIN AUTH: http://localhost:9599/?ALLOWED=ABC?&GUID=76561198031767071&PSW=
AUTH PLUGIN RESPONSE:
OK|Welcome!
PLAYER AUTHORIZED
ENTRY LIST OPEN MODE 1
Looking for available slot by name for GUID 76561198031767071 supercars_holden
Looking for available slot
Slot found at index 8
ResetCarResults, index: 8
DRIVER ACCEPTED FOR CAR 8
DRIVER ACCEPTED FOR CAR Bogor
Tyre blankets: false
Sending SESSION ID : 8
Sending type 2
Sending type 3
Sending ID : 0
Sending type 2
FIND AND SEND PLAYER'S POSITION
ELAPSED=506118
Sending 4 checksum requests
SERVER TIME: 1198244
DRIVER: Bogor []
OK
TCP packet 67
Dispatching TCP message to supercars_holden (8) [Bogor []]
Clean exit, driver disconnected: Bogor []
OK
read tcp 172.31.1.183:9603->110.23.156.140:59887: wsarecv: An existing connection was forcibly closed by the remote host.