Airport keeps falling out

Hi!

For quite some time I´ve had problems with my airport, and I´ve found what seems to be a pattern in how it works.

If I´m using internet for normal surfing, checking news and email everything works fine, but as soon as I try to watch a movie on Youtube or something like it,

the airport drops out. I wondered if anybody knew what could cause this. I´ve had a new airport cart installed without success also.

I'm using an old MacBook with a 2 Ghz Intel Core Duo chip.

Best wishes,

Oyvind