I'm also having this along with many other issues brought on by the 4.3 update. Unfortunately, there are no announcments for a fix to these issues. There are many frustrated users out there experiencing much worse (including myself). See below for a short list of 4.3 issues:
Major issues in new Android 4.3 update for Galaxy S III:-
- Wake up lag (Sometimes it takes a few seconds to wake the device from standby and sometimes a few minutes)
- Random Freezing
- Huge battery drain
- Bluetooth Audio issues during playback in car
- Stuttering music playback with stock Samsung music app
- Device freezes as soon a call is received (Black screen issue)
- Poor RAM management (very difficult to multitask)
- Wi-Fi issues