Is it possible that your computer has become a Skype Supernode and it is related to all the connections?
Skype is a shared app like a P2P file share app. If it is running all the time and you have a reasoanble Internet connection and a faster system, Skype will start to route user calls through your connection. You become a Skype supernode. I found this on my home system where it was always running
This is some info we found related to some research by a University Can't find original info at the moment
Skype uses a node-base Peer-to-Peer Model, where individual clients perform some processing tasks on behalf of the network . This model allows for "Supernodes " to be created. Supernodes are where individual computers begin to route a sizeable amount of 3rd party traffic, 200MB per hour has been detected on the some networks from the Skype network. One study has measured a supernode over a 24 hour period to log 319,314 flows to and from 38,366 IP addresses.
The way Skype functions is that each node can handle the calls of any other user. Some systems will become a super node and handle tens of thousands of calls, all for otehr users. This happens when a Skype client runs all the time and has a good connection. Not sure how the determination is made, but it happens. You then have lots of network traffic and hard drive action for these calls. Try exiting(Quit) Skype when not in use. Not just minimizing. I had this issue on a desktop that ran all the time and Quiting Skype solved the issue.