I seem to have the very same problem on my desktop ever since it auto-updated to 38.2. The worst thing is that while it stops responding and basically hangs, the system doesn't recognize it as frozen. So it's quitely sitting in the background pretending to be checking my emails...and then, perhaps hours later, I find out that it's in fact frozen and while it was frozen, I've received plenty of mail. And when that mail is something important, this can get really annoying really fast...