It happened to my old forum actually. My host said it was malware but it wasn't. I found out who the hacker was and gave him a little of "my cup of tea" if you know what I mean. ;)
The reason that happens is because sometimes you are running too many native apps in the background of your computer. Other times, you may have a virus or malware stuck onto your computer.
Shit. I'm dead. :P
ISP companies should seriously do something. I don't pay them $100 bucks a month for them to sit there and think their better than me at networking.