Hey.
This seems to be a common issue.
I've seen mixed posts on the net about the ES8000 working with the Apple Keyboard but from what I've seen the Apple mouse tends to fail the sync constantly.
Sad, I just bought a mouse to improve navigasting on the ES8000 and dissapointed that it doesn't sync. Maybe an issue with drivers on the TV.
Which Dell mouse (model number) works for you?