For starters, this only happens on World of Minecraft servers.

Whether I use the browser or the client, when I log into a World of Minecraft server, it works fine for a few minutes, but then it starts to lag my entire PC horribly. I'm forced to open the task manager and close out of either my browser or my client, whichever I'm using, and things are so slow that doing that takes a good ten minutes. I've searched around and I can't find anyone with the same problem. There is no error message. It's not OpenGL either, I tried that solution and the problem persisted. I tried to get on with my friends laptop, and that worked, but I can't put the client on it and it's hard to build with a laptop anyway, so I need to get my PC to work. Any help would be most appreciated.