Cryptic, the dev studio behind Champions Online, Star Trek Online and the upcoming MMO Neverwinter, has just released a notice that some of their servers that contain users' personal information were hacked in 2010 and that the encrypted data had been compromised. But the good news is that if you follow good internet practice and have changed your passwords sometime in the last two years, you probably don't have to be worried by the bleak letter that just appeared on Cryptic's website, or the cautionary email you may have just received.
In their letter and the email (which I received because my account was one of those compromised--thanks, hackers!), Cryptic stresses that they only have evidence that account names, handles, and passwords were stolen. They do not believe that billing addresses, email addresses, date of birth, or credit card information was compromised. All affected accounts have had their passwords reset--so that might be why you're having trouble logging in right now.
If you have a Crpytic account, make sure to check your junk mail inbox for a warning to see if your account information was stolen. And even if it wasn't, it's a good idea to change up your passwords--especially if you're still using the same one you did in 2010.