Question for computer experts!!!?

I've noticed lately from looking at my firewall logs that my computer has been trying to send UDP packets to an isp called Chinanet. It does this everytime I'm on it. It tries to send the UDP packets through some ports called netbios -ns. This doesn't make any sense! The only reasonable guess I have is an infection. The thing is, I've scanned with my AV and three free scans which are Ewido, Onecare, and the Kaspersky free scan, all of which picked up absolutely nothing! My computer hasn't even been acting strangely! Unless there's a such thing as an undetectable infection, with no symptoms whatsoever, that four scans do not catch, an infection seems unlikely. I never even download anything, and I've never even heard of an isp called Chinanet until now. Has anybody even heard of something like this? Any answers appreciated.