Last night at approximately 0515, I was booted from game because someone used my account credentials to log in. I have immediately changed all of my passwords. Given the level of encryption and the types of software that I use, it is highly unlikely that my machine was compromised. That only leaves Cryptic's account server and given it's dodgy past, you may wish to consider changing your passwords as well.
I have advised Cryptic of the breach, but I thought that I should give a heads up here as well. I suggest using upper and lower case characters, numbers, and other characters such as the pound sign and exclamation point as they are not routinely used. Hopefully, you can avoid any unpleasantness in the future.