Time lapse fails after a few hours

I apologize if this has been answered before...

I have a brand new 2tb sky+hd box, being a new installation just last week.

I am used to time lapse on Tivo previous to this.

This is the problem I am having...

I pause live TV for a random time (lets say 60mins) then I unpause and now watch it 60mins behind live tv. Around 2-3 hours later it just pauses all by itself and in the bottom left of the screen it tells me to press 'Sky'. At this point I cannot resume or fast forward, just rewind. If I press Sky button it just jumps back to what is live.

Is this normal behavior for a sky box?

TIA
Leigh