I had that problem bad..for awhile until I went to one of the newer Carbon nightly's then it just went away. Disabling hw overlays helps for awhile on other roms then you get a RR ....I don't know but carbon seems to be running the best (for me) the last month or so that I've had it on here and I've used 2 dif nightly's so far.
This problem has been my biggest issue on this phone. Its always on lock screen only right after waking the phone and then it stops after actually unlocking with the swipe. Nice to see that I'm not the only one.
Sent from my unlocked Solavei, SAMSUNG-SGH-I717 running Carbon and Uber kernal with ICS blaze modem using xda app lol
i717, Carbon, Beanstalk, JB Sandwich,
Liquid Smooth, Cyanogen, Slim Bean
Love setting up a fresh install