Why does my macbook intermittently lose internet connection when I have internet service?

Hello,

I have checked around on Apple forums as well as the wider internet. My situation is just a bit different than the other solutions I read about.

I have a MacBook, 10.6.8. I have an internet antenna that plugs into the modem, that I plug into my computer. What I have not found in the forums are solutions to an internet connection loss that happens with a hardwired internet connection, ie ethernet wire, not wireless.

I contacted my isp and I was told there is a very strong connection. The internet will cut out when I open another window or just at random times, maybe for 20 seconds. This is very irritating.

Skype and itunes run just fine even when the internet cuts out. I feel there is a problem with one or my of settings. Any help is greatly appreciated.