Arch Linux drops me on my school network [closed]

I'm running a Lenovo X61 which I carry around my college for getting on the internet at various points in the day. The network has always been finicky but recently it's gotten worse. I'll connect using iwconfig, get an IP from dhcpcd and log in using vpnc to their system. Sometimes I'll stay connected for hours but most of the time within 30 seconds my network traffic will drop to zero and I'll be unable to do anything

My computer still believes it's connected, however to try again I need to put my wireless interface down, put it back up and try again. It's gotten so bad that I've got a window on my computer pinging Yahoo or Google constantly in order to know if I'm still able to get online.

I know other people who have used Arch Linux that don't have the same problems as well as people who use Ubuntu who haven't had any problems either. It seems like my computer is a special case. Does anyone have any suggestions on how to fix it? dmesg doesn't show anything out of the ordinary going on and I don't know where else to look for errors or other things to try.

Edit: this doesn't happen on my home network. It's a problem that only happens at school.

This may not help, but I thought I'd let you know. My z61m thinkpad has the same problem, but only with one of my two access points at home. It just started happening out of the blue. It had been working fine with both access points for about 6 months. It has the identical problem in either windows, linux, or OpenSolaris. Both access points are made by D-Link, but they are different models. For that z61m laptop, I've simply been using the access point that still works OK. I suspect the wifi card in the laptop but I haven't proven that.

I would take a look to the power management: I suppose that when the pc goes idle, many softwares and devices could stop working (I noticed that behaviour on my machines running Ubuntu 9.04 and ArchLinux); I meant, try to disable all the power saving features from your OSes, and see if it happens again.

Just my 2 cents.