Hi James,
I just double checked on my Spectre -- the "HP Truevision HD" camera is listed under the "Imaging devices" and so far I didn't see it "disappearing".
I'm not using the touchscreen much, but as far as I can tell I never noticed it stopping working. In your case might either be an hardware issue, or a conflict with some instsant messaging software you might have installed.
- Adriano