I'm pretty sure that the original Airport card can only support WEP. I think the issue is that WPA/WPA2 require at least 11g. The original Airport was 11b.
I run a dual-USB G3 iBook on OS X 10.4 and I cannot connect onto a WPA/WPA2 network. I'd have to knock my network down to WEP for it to work wirelessly. So I just use Ethnernet on it.
Not sure if Unbutu can get that card up to WPA. At the very least, couldn't you use a USB wifi adapter? Of course, most of those require USB2.0. Alternatively, are there any 11g/WPA ethernet bridges?
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