I'm experiencing very slow connection last days over a wireless connection.
I have a rt2500 based MiniPCI on a MSI laptop, and a IskraTel Sinope ADSL modem which has an option of Wireless. Now I can turn it on as a Wireless router or use it as a Wireless modem. I'm not using the Wireless router option because port forwarding on this crappy modem is a headache. So I'm using it as a Wireless modem, connecting to it over wlan0 interface and then I have configured rp-pppoe to connect to the web.
Now this configuration has worked for me for very long but lately I get very low speeds(pings are ok though) on the web and local network, and my wireless signal just suddenly drops, so it disconnects me, and then comes back again for a few seconds and the story continues.

I also have a Slack 12 box with a rt71 based wireless USB key, connecting in the very same way as this laptop and it's connection is great, so I don't think this could be the modem. I've checked the logs, nothing special just rppppoe says:
dmesg doesn't show anything unusual, just:
This was happening on 2.6.23.1(was working ok here before) and now I've compiled 2.6.23.9 kernel and recompiled the wireless driver which I obtained from http://rt2x00.serialmonkey.com and this problem just keeps reappearing.
I haven't changed anything on the system or that I would know of any change by the time this has started happening and I have no idea why this is happening.
I hope that anyone knows anything about this and can help me.

What's the link quality when it drops you? That's what the issue sounds like to me. Maybe your neighbor got a fancy new microwave or something interfering with the waves..

All the neighbors are minimum 10m from our house, so I don't think this is it.
The Link quality before drop or at slow connection is 8-12%, but the quality never exceeds 20%, which is normal as my room is quite a long way from the room where the modem is.