From the article:

The Justice Department said it had investigated and found no basis for concerns voiced by Google that a new search box included in the Internet Explorer 7 browser would give an unfair advantage to Microsoft's MSN search service.

The article went on to recap Google's argument:

Google spokesman Steve Langdon said on Friday that Microsoft is unfairly setting up the search box within the new Internet Explorer so that it defaults to MSN's search service when users type in search terms -- rather than allowing users a simple choice of search providers.

"Changing the search engine may be simple by Microsoft's standards. But if it were truly simple, users would be able to change the default with one click," the Google spokesman said.

"Microsoft could have easily designed it that way. Instead, they've built it so users have to go through multiple steps to choose a search engine," Langdon said.

I don't have Opera installed on my system, but I did run a quick check to see how Firefox works this issue out. Right now, Google is the default search box, but I can click on a drop down menu and choose to run the search on another engine. I ran a search on Yahoo! and sure enough, the search box did stay with Yahoo! after the search. Even when I launched a new browser window, Yahoo! remained the default browser.

That said, I've heard from numerous folks that it's darn near impossible to change the default on the Mac Safari browser...so I'll stick with two words to describe the Google complaint: sour grapes.