I've decided a few days ago that in order to improve the security of my wireless network, I should change the encryption of the network from WEP (which can be decrypted in under 60 seconds, that's proved), to WPA (which can resist even a year to a decryption attack, experts say). The reasons was that I had some doubts about the devices operating on my network, but everything is clear now (I have over 10 devices usually connected on the network).
I have two Asus routers, a WL 520GU one (with print server), and a WL 520GC one. I've written some time ago an article on how to set up WDS (or Wireless Distribution System) between them (a method of improving signal into your house for example, by setting them to operate in the same way, under the same name), which is available here (it should be applicable to almost any other models of Asus routers).
So, let's return to the problem from the title. I've changed their both encryption method to WPA, and I've let them continue working. Everything worked smooth for a few tens of minutes, than my devices were disconnected.They reconnected very fast (a few seconds), and continued working, again, for a few tens of minutes.
Then, suddenly, the entire network crashed, all devices were disconnected, and all tries to reconnect failed, as the main router (from which comes the internet connection) was refusing to give addresses to the devices requesting them. I said that it refused to give addresses, because it is practically the one doing the whole job, with the second one only repeating what it "says" to the network. As I wasn't able to receive the addresses, there was no possibility of getting into the routers in order to check the reports to see what could possibly fail like this. A restart of the routers (disconnecting their power cables) made the network start working again (this happened somewhere around 1:30 A.M. in the morning).
And they continued working until the following afternoon, when the network crashed again, creating exactly the same situation. I've searched for an update for the firmware of the routers, but there wasn't any. I've also searched to see if somebody else was having the same problem, and I found a few users reproducing quite the same situation, but the provided fixes were not helping at all.
I changed the encryption back to WEP in that afternoon, and everything has been working perfectly since then (very stable). I can't imagine what could be the problem that caused that crashes, probably that there's an incompatibility between these routers when they're operating in WDS while encrypted with WPA.
So, I repeat. If your Asus WDS crashes while secured with WPA, try changing that with WEP. Hope this helps you.