Google Reader scrolls to the top of the articles list when selecting an article. This makes reading articles "below the fold" (i.e. ones that you need to scroll down to see) very annoying, as it scrolls up to the top (thus hiding the article) every time you click on a new article.
1. Have a large number of unread articles in Google Reader (enough so that you need to scroll to see them all)
2. Scroll down
3. Click on an article near the bottom of the screen
The article list is scrolled up to the top, hiding the article you just opened.
In step 2, you must *not* scroll down all the way to the bottom of the page. Things work correctly in that situation. So, you must scroll down to somewhere in the middle of the page.
Bug 13425 seems like a related issue.
This now works for me. It may have been fixed on Google's side.