I have an access point running on Linux 2.6.22-gentoo-r9 with madwifi-ng 0.9.3.3. Lately I bought a Nokia E51 cell phone which has WLAN integrated. After a short time browsing the web, page loading became very slow. With the phone comes the VoIP-application Gizmo, which wasn't able to connect at all to its server over WLAN. I switched off power-saving in the phone and suddenly everything worked fast and Gizmo could connect to its service. A reboot of the AP also makes the phone (in powersave-mode) work perfectly - this solution only lasts for about five minutes though.
Considering power saving in clients and getting worse over time, it looked to me like the stuck beacon problem, but I can't find any error messages about it in my logs neither can I say that my interrups go higher (they stay at around 40 per second).
I tried all the fixes on the Stuck Beacon page and in ticket #1081 - nothing helped and running the phone without power-save mode is no option as the battery then is empty in less than half a day.
Other clients don't seem to be affected, it's only the mobile phone that can't use network connectivity any more - and switching it to 'no powersaving' while the problem exists solves it.
Unloading all modules and reloading/restarting networking and hostapd didn't help either.
btw - I found reports from people having the same problems with Zyxel or Linksys routers: http://www.allaboutsymbian.com/forum/showthread.php?t=50908
