Unable to connect to Wireless Network

Hello,

I have an intermittent problem with my wireless network that is annoying the heck out of me. Here is what happens:
1. I'm on the network and everything is fine (network show up as green - full bars)
2. Suddenly, I am disconnected from the internet and this green network icon button turns yellow.
3. Double clicking on the yellow icon opens the INtel PROSet/Wireless WiFi Connection Utility".
4. In this window, the network shows as available.
5. The utility is set to "WiFi On" (bottom left of window)
6. When I click on the network (which shows up with 5 green bars), the system says, after a 10 second pause, that it is "Unable to connect to <<MY Network Name>>.

I am dumbfounded as the only way I can get the network back is to reboot/restart the computer. When I do this, the wireless connection works no problem and I am automatically connected to the computer at start-up.

Does anyone have any idea what is going on here? Why am I thrown off the network suddenly? And why can I not simply get back on by double-clicking the network inthe Wireless utility.

Thanks.
Peter from Seattle.