I have observed this behavior again today, with the updated version (16.1.0.33) this time.
After being left idle for a couple of hours, I return to the desktop and find the ccSvcHst.exe using all the CPU it can get. No errors are logged, no tasks are apparently running, or logged as running. Updates and Pulse updates are being applied normally. Nothing is logged in Event Viewer. My computer is slow, but responsive, but this is probably due to the fact that I have Core 2 Duo and 2 GB of RAM.
The only way to stop this is to reboot the computer. And it only happens from time to time.
The only additional data I can give to you Symantec guys is that the module that is causing this is msvcr80.dll , the name of the thread is !endthreadex and it was running in the ccSvcHst.exe process that is running in Session 1. I have a laptop, andf it was running on AC power, connected to a wireless network with another XP Professional SP3 computer and a shared ADSL connection.
Needless to say, I'm puzzled.
I have Vista Home Premium 32 bit, and it is absolutely malware free.