DigiNotar's servers were compromised several weeks ago, with hackers obtaining access to hundreds of certificates.
That part of the article is completely wrong. The actual facts are:
* hackers compromised DigiNotar's servers
* the hackers generated hundreds of brand new perfectly valid certificates, for popular websites, including google.com.
* traffic for hundreds of thousands of computers, mostly in Iran, were directed to servers controlled by the hackers, using the hacked certificates
* the hacker could have accessed usernames/passwords/credit cards of anyone who accessed a website via their servers
* since the hacker may have your gmail username/password, they can probably gain access to almost any other account you have and perform identity theft, etc
This is a very serious attack, fortunately it's mostly only effected people in Iran.
The hacker has claimed to also have access to four other un-named certificate authorities, and has promised to do even worse stuff next. He's probably telling the truth.