Was there anything else in the PM you got? If you got banned for something like plagiarism or spamming, it will tell you exactly that. If you got locked out for security reasons, like failing the security question when trying to log in, I'm not sure if they tell you that. From what you wrote, it sounds like it might be something like the latter and hopefully for your sake it is.
The good thing is that if you did just get locked out, account recoveries are supposed to be much quicker these days. If it was about 6 months ago, you could pretty much kiss your account goodbye.
Edit:
I don't think it's a PM, it's probably shown on the screen when the OP tries to log in.
Ah, gotcha. The coffee has not yet kicked in, apparently. And good luck to OP. Sounds like he wasn't banned, just locked out for whatever reason.