Airport connection problems

Maybe it's a hardware fault, but from what I can gather it seems that it would be a software problem!

The problem, it seems, is that the Airport app is effectively going to sleep after loading something. For example, when I go load a webpage it doesn't load until I click on the Airport icon in the Finder bar and the status changes from 'Airport: On' to Airport: Scanning...'

Only when I manually open the Airport menu (or 'wake' it as I see it) does it connect and work for me. When I wake Airport, however, it only lasts intermittently. For example, if I am watching a video every time I open the Airport menu it will load approx. 30-40 seconds of video and then drop again.

I scoured the web for solutions before I posted this, so I hope you can help!
Sorry if I'm stupid and that this is a hardware issue, seems to be software to me!

I'm running OS X 10.5.8

Thank you!

If I have strange Airport behavior the first thing I do is turn off all WIFI encryption and create an open network. If the issues still persist I will delete my Airport interface in the Network Preference and re-add it. The only bummer here is that all the previously remembered networks are gone with it, so if you travel with a laptop you might be annoyed by this behavior.