upgrade to 2.2.1 now missing sidebar & footer

I just upgraded from WordPress 2.1.2 to 2.2.1 and now my blog doesn’t show its sidebar or footer. I created a new post but this doesn’t show up to the general reader. In fact, some of the old posts have “500 Internal Error”. I tried to undo all changes with my backup but got more errors. So I’ve redid the upgrade and am back to missing parts and post errors. Where do I start to fix this?

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