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Well... the first thing I'd do is recompile the kernel, using the internal drivers for Prism 2.5. I've got 3 of those cards in 3 different computers (two Linksys WMP11, and one D-Link DWL-650), and in all three cases (well, both) the Kernel driver has worked the best. With the kernel driver, the device will be detected and installed as ethX. eth1 in my laptop, eth0 in both of the desktops because those two don't have an ethernet card.
When it's detected/installed as ethX, you just need to edit /etc/rc.d/rc.wireless.conf with the appropriate information. Static IP if you have it, ESSID, network key, or whether or not to use DHCP. All the routing information/etc is set up automatically when you use DHCP, and I'm guessing that the rc.inet1 script (which calls rc.wireless to bring up the card in question) will set up the appropriate information if you're using static, too.
It's just a guess, but I have a feeling that if you set it up that way, your problem will magically disappear.