minecraft server issues

i recently set up a minecraft bukkit server for me and my friends to play on. everything went fine until i tried to set up a custom ip. It works for the most part, except the fact that itll give me this error "Internal exception: java.net.socketexception: software caused connection abort: recv failed" randomly when im connected through the custom ip. it also happens when i connect through my ip. It works fine if i direct connect through localhost.

So, how would i go about fixing this?

I did some thinking and i thought of some possible reasons why this happens:
1.) I have a dynamic ip
2.) I have k9 web protection installed on my pc

I also get this error when i connect to other peoples' servers, but not on my other pc. That pc can connect to my server as well, and has no problems. that pc doesnt have k9 installed though, so i think that might be the problem, but idk

any help would be awesome, thanks!