Using a Task killer cause more problems than not using one. You
can read the following post to see why :
Why you don't need a task killer
If you still want to use it, exclude Beautiful Widgets or Plume
from your task killer. Otherwise it is killing the background
services which are then unable to update the application.
Please note that even if it was excluded before, you might need to check if your task killer still does it, sometimes an update can break the exclusion.