On our end there’s not much to help you with – we can just speculate around what’s wrong. I mean, I can’t know how or why you’re sending bad packets for sure, but I do know that when you send them the server takes security measures against them.
Generally, bad packets are sent when people are using external programs that interfere with L2 trying to Bot or Hack, so I have no idea how this can be happening on your system. UNLESS :O (j/k lol)
After the Virus scan finishes let me know if it blocked any files in the L2 directory (or any other items – even irrelevant).