I've read a bunch of forum posts about the Android OS battery drain bug. This is where the Android OS process is showing large percentages in the battery statistics.
The fixes suggested so far are:

1. Reboot (Temporary).
2. Turn off and remove battery for a couple of minutes.
3. Reset battery stats.
4. Change WIFI sleep policy.
5. Use a task manager
6. Flash stuff to the phone.
7. Revert to older versions of the OS (not really a fix).

Does anyone know the definitive cause of this problem and the correct fix? Or is it possible there are multiple issues that cause this so different things will work for different people?

Here are some of the threads: