What's at fault -the router or adapter?

Been having problems with my wireless network on and off for years. Fought with service provider thinking it was them. They did find some line problems outside home, but issue still continues. I have 2 XP sp3 systems and 1 Vista laptop, DLINK DIR 655 router and a Linksys WUSB600N ver 2 adapter (dual band). Both are highly recommended. One or both of these must be the problem. How do I determine which one? I've checked the drivers and they both are up to date. I video stream a lot and the stream just stops dead at times. Even normal web pages load slowly at times. This does not happen when I bypass the router and connect directly to modem. Please advise.

sounds like somebody has a wireless tv camera nearby, or a wireless phone. these interfere with wifi.

So, how do I fix it? Are there any settings I can change to prevent this from happening? Are newer routers better at blocking interference?