I've already run into this virus twice in my travels, both times the infection came though emails claiming the attached file was a returned check from the bank. One of the infected systems was shut off as soon as they saw the popup, it seems the virus started encrypting the recycling bin first, so they didn't lost anything important. The other had an offline backup I just restored the system from.

By the way, both systems had up to date AV, one had MSE, the other was running Avast.

I have a few offices that have to use older versions of IE (8), so I run HitmanPro.Alert on those systems to help prevent the browser from being exploited. Noticed the other day they released a version that is suppose to block cryptolocker and the like. It's free and literally takes 2 seconds to install. I tested it on a test system I intentionally infected with cryptolocker, and even though the virus was able to run(no AV on test system), HitmanPro.Alert popped up an alert and the virus wasn't able to encrypt any of the test files on the system.

Here's a link if anyone is interested -http://www.surfright.nl/en/cryptoguard

I also second Bert about MBAM (Malwarebytes Anti-Malware), detection rate is hard to beat...