Wireless D-links card,,,anything any better?

I have a D-link DWL-G510 network card in my sons computer. It is approximately 40' from my office computer, where I have a D-link DI-624 wireless router. This is all on the same level in the basement, and is acutally only going through maybe two walls(if you dont count the open doorway to the office). His computer has worked intermittantly, with the dsl service, sometimes he's on, sometimes he's off. I just upgraded him to a new Dell system, and switched the card over, and was surprised that it is the same. I forgot to mention, he hasnt had internet access with his old computer for over a two weeks, and changing to this new Dell didnt help(previously, he had been able to get online, but not on a consistant basis). We always get the message "network cable unplugged ", but I know it isnt , the card is in the slot, I even took it out, and reinstalled the driver, etc, plus, unplugged the wireless router, and repowered it, but that didnt help either. So, Im thinking maybe the wireless network card, just quit, and if so, I think Ill go to another brand, as that thing hasnt worked correctly from the word go. Any ideas, or recommendations?
thanks,
coadman

 

some questions?

2. what's a "nic "?
3. define "differant channel "?
thanks,
coadman