I was starting investigation and figure out that my problem was the same as this. There is also workaround solution was found. First, let me describe my hardware and symptom data.

I have usb wireless adapter D-link DWA-110.

#lsusb
....
Bus 002 Device 004: ID 07d1:3c07 D-Link System Wireless G DWA-110 Adapter 

Linux kernel:

# uname -r
2.6.30-1-686

Sometimes I observed that my network going to hung. In my logs I observer such messages:

Dec 22 21:45:36 agrytsenko kernel: [52190.300066] wlan1: no probe response from AP 00:26:5a:95:8b:cc - disassociating
Dec 22 21:46:56 agrytsenko kernel: [52269.860040] wlan1: direct probe to AP 00:26:5a:95:8b:cc try 1
Dec 22 21:46:56 agrytsenko kernel: [52270.060080] wlan1: direct probe to AP 00:26:5a:95:8b:cc try 2

I have written little script which restart my network:

#!/bin/bash
ifconfig wlan1 down
sleep 5
iwconfig wlan1 essid amber
iwconfig wlan1 key s:apple
iwconfig wlan1 rate 54M
ifconfig wlan1 up
dhclient3 wlan1

But this way is not good idea at all. So after googling I find next solution(it’s also not complete solution, but quite better then my previous). This solution involve kernel sources. Therefore you should download it. After downloading you need to compile and install new kernel. Here is good how to for Debian users.

Before you begin to compile new kernel and after unpacking the sources you should change one line in your sources. First, try to find it:

cd /usr/src/linux
# grep -r IEEE80211_MONITORING_INTERVAL *
debian/linux-image-2.6.30/lib/modules/2.6.30/build/net/mac80211/mlme.c:#define IEEE80211_MONITORING_INTERVAL (2 * HZ)
.......

So our line is found. Go there and set value to 100. Ex.:
from

#define IEEE80211_MONITORING_INTERVAL (2 * HZ)

to

#define IEEE80211_MONITORING_INTERVAL (100 * HZ)

After new kernel installed and loaded my problem disappeared.