Am unable to connect to the internet for more than a couple of seconds
 

Hi, I've recently installed Arch Linux, and I have been having problems trying to connect to the internet. I have a Realtek RTL8187B wireless card, and a WEP encrypted router that I am trying to connect to. My linux version (2.6.28) is more than sufficient to support this wireless card (or so I am told), the driver is loaded, and I have been able to connect, but only for about 2 to 3 seconds. My main method of connection has been:
ifconfig wlan0 up
iwconfig wlan0 essid <ESSID> key <WEP KEY>
dhcpcd wlan0
And to test this, I just ping google, which works for about 2 seconds, at which point it stalls and eventually times out. Any other attempts to connect to the internet are similarly greeted with long stalls and eventual timeouts. I'm not at all sure how to tackle this problem as I am still pretty new to Linux. Thanks for any replies.

try to disable WEP, to see if this makes any difference.
Any pointers in the logfiles ? (router, syslog ....)

I can't disable WEP on the router, because I am not the only one that uses it. As for logfiles, I can't see anything relevant. The problem, though, seems to have become worse. Now I can't actually connect at all, as dhcpcd is unable to get a lease.