I've been fighting this today with my Helix LT! Really annoying. After a few minutes of recording stereo track over USB the audio becomes delayed by more than a second.
Stop/play logic resets it.
I have found that the sample rate in the Helix is 48kHz and in my project in logic it was 44.1 kHz. Changed the Logic Project->Audio sample rate to 48kHz and have now had more than an hour without the issue.
Hope that helps someone...
Mike