A Google News Help thread has several reports from users that the Google News homepage "flashes" and "jumps" when you scroll through the news.
I was able to reproduce the issue while on Firefox 11 on my Mac. It in fact does jump, when you mouse over a new block that tries to, for some reason, expand, but that only shows white space for a second.
I captured it in a video:
Erik, a Google News representative, has confirmed the issue. He said:
The team has been made aware of this issue, and it's being looked into.
Google has not given an estimate time for a fix.
Forum discussion at Google News Help.