Problem: Weird and random wlan router.

Ok, so here's the deal. About four months ago me and 5 of my friends bought a wireless lan router with built-in ADSL2+ modem. We live 3/3 in two appartments on top of each other and we figured a wlan was the best way to go since we wanted the same network in both appartments and be able to use the same internet connection. The router we got was a Telewell TW-EA510. It worked great for about a week, then we started having problems. Every second day it had to be restarted. IRC, SSH and games would work fine but when trying to access web-pages nothing happened. It was very strange.
After we updated the firmware a couple of times and re-checked the settings at least a dozen times things seemed to be better, restart needed perhaps once a week. Until now.

Since we got back from the holidays the router has really been messing with us. One of us is connected via cable to the router, everything works fine for him, but the rest of us are screwed. You can find the wlan, great signal strength and all, but when you try to connect to it nothing happens. The "Wireless Network Connection" screen pops up and "Waiting for the network..." starts rolling. After about 20 seconds the window goes away and now comes the weird part; it says that you are "Not connected" but everything works fine! IRC, SSH, web, games... you name it. But after just a couple of minutes the "non-existent" connection fails and we're back where we started.

We don't know what to do, it seems like we've tried everything, updating the firmware, resetting to factory settings etc. etc... Also, it doens't seem to be a windows error since some of us are using linux and it's the same for them. The worst part is that it's acting so randomly.

Please, if you have any idea what's going on here, tell us!

Thanks for reading.