This stuff works well to remove paint, and it does not harm plastic.http://www.hobbylinc.com/htm/flo/flof552144.htm
I've used it with success on 50 year old paint. A friend of mine says it works well on permanent marker.
I should've posted about it sooner, but I didn't think about it until I read your post just now.
You may want to check you local hobby stores, they probably carry it. The link is mostly so you can see what it is I'm talking about.
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Macs liberated: 2
Macs Owned: 3
Cat vs. SE