Ok Relic I got the file, to me it looks pretty clean as far as spyware goes. I have another question for you.
You said that you have a cable modem, do you also have a router? This may be another thing we can look at, "firmware".
Firmware is software that is embedded into the hardware. How old is the modem and what kind is it, maybe if we update the firmware this may help.
While it is true that with a cable modem your signal strength will degrade during high usage periods, I am leaning towards something else, I personally have never had it drop below 3Mbps during high use. Meanwhile there are a couple of tricks you can try, go to Start, run then type in dxdiag. Let it load and click the save all information button, save it to a place like desktop. This is what I would do to test it out. I would go to sound then I would set the acceleration down a couple of knotches. Something is taxing the system resources IMO. How much memory do you have, and how close is your hard drive to being full?