Thanks for your help. In case someone else runs into something similar, I figured I'd post my results.
I finally got the client working. Turns out 0.3.5 was just buggy (surprise!) and wouldn't connect to the network on my system. I know the passphrase was correct, because I was copy/pasting it from a text file to be sure. But apparently the client needed to talk to the network and was having troubles (lots of IOExceptions).
I upgraded to 0.3.10 and now it's working! Now I just need to get some BTC transferred so I can buy NXT and start mining. Or if someone reading this is feeling generous, then I'd be pumped to get any NXT donation, no matter the size...

. Pretty please!
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