Using OpenWRT with WPA-PSK 2 on Broadcom WLAN routers have been stuck on a quite old bug. Recently someone suggested that it may have been fixed in trunk, which caused me to test it. And it works!
It took some time to work out the details here. To save myself time to reconstruct the commands, and hopefully save you some time too, I wrote down how to use OpenWRT with two Asus WL-500g Premium linked together wirelessly using WDS and PSK2 encryption.
The writeup is long, so I put it on a separate page:
http://josefsson.org/openwrt/wlan.html.
If you are interested in using OpenWRT with a 3G connection, you may find my summer house internet writeup more useful.