Aunque esta en inglés esta muy facil de entender:
(SIN INSTALAR NADA, ni la actualización KB975777)

Windows 7 error 'Host process for window tasks has stopped working"

Solución Error Windows 7 "task host windows"

The cause of this error that appears from time to time with Vista and also in Win7 Beta is not clearly identified and explained by Microsoft, but it is possible to correct the error.

1,. In Control Panel (Control Panel), select all the elements (all Control Panel items), then Administrative Tools (Administrative Tools).
2.- Select the Task Scheduler (Task sheduler), then the Library Task Scheduler (Task Shedule Library)
3.- Deploying Microsoft Windows, and then click RAC
4.- In Display (View), select Show hidden tasks (Show hidden tasks)
5.- In the right-click on RacTask, select Disable (Disable).

The error message should no longer appear.