Wireless HIGH ping

Hi

I have a network at home with 2 pc's. They are both connected to the internet with a dsl router.
The laptop is connected with a Siemens PCMCIA card and the desktop with a Linksys USB adaptor.

Some day I was playing multi when I saw that I have some lag on my connection. Opened a console window and made a ping -t that gave me 50ms +/- until, after 60 sec, it reply 3500ms +/- and then 50ms +/- back a again... etc... etc.. after every 60 sec a reply of no less than 2800ms.

What is appening here?
Can someone help me?

Thanks in advance...