And it strikes again.. I saw on some old post that you Jit said to turn off firewall, and a friend also told me that this could help to stop these black lines on netgraph, but is that safe to do ? Will my pc be exposed to unwanted things if I turn it off ?
It will be, but for the short period of time that you'll be doing it, it won't be an issue. If you're worried about it just close everything you have running, and only run paintball for the time you have the computer firewall off. Also, what is your network structure at home? For example, computer -> network switch -> router+modem in one -> interwebs or computer -> over wifi -> router -> modem -> interwebs, etc. Asking this because you didn't specifically answer that you tried this, but if you have a seperate router and modem as jitspoe suggested above, the router will have a firewall built in that might be also causing issues, and since they are seperate you can bypass the router firewall easily.