Google has not liked redirects for a long time, but usually they could only catch the META REFRESH redirects. There's been rumor lately that the spiders are starting to be able to figure out other types of redirects as well. I've been using a hahahahahahahahahaha redirect for eons now and recently I've had a few pages that ranked very well just up and disappear. They still have a great PR (PR5 and 6) but they just don't appear in the SERPs at all. I'm thinking they've caught on to the trick. In your case, while you are not trying to deceive the GoogleBot, the bot itself really is not smart enough yet to determine if your redirect is malicious or not, so it just assumes that you're trying to trick it and penalizes you anyway.
Funny how SEO always comes back full circle. More and more lately, getting great results that STAY great results is just a matter of going back to the basics and trying to get rid of the people that use shady tactics to move ahead of you. I've spent a lot of time lately just building good quality pages with relevant links and as time moves on I'm starting to see some good results again, with pure organic SEO and no tricky bullshit. Go figure!
