I've learned the hard way that D-Link products just aren't worth buying. I have a 802.11g router, that will overheat even in a 65 degree house with one computer connected to it, and just web browsing. It overheats, and then reboots itself. Apparently it's a well known condition with that particular model.

I also have an older 802.11b wireless card for a laptop, and that thing is also a turd. I killed about three D-Link routers in a row at work, trying to simply update the firmware... So, after all that, I won't buy another D-Link product again.

From what you describe, I might suspect that your router is at fault. If possible, borrow a different brand from someone for a couple of days, see if the problem persists. If it goes away, chuck the D-Link router, get something else (I'd recommend Linksys or Belkin myself). Otherwise, the other likely scenario is you have a spyware problem.