Software version 5.08 arrived not so long ago and now version 5.09 has started to roll out, appearing on my 360 boxes yesterday. This can only be another minimal update as I have not noticed anything...
I'm still on version 5.08 but this has happened to me a few times, on this and previous versions.
On a side note, go into the 360 Settings > Audio & Video and either go to Change TV set up or Change amplifier /pair remote to audio system and see if there are still two keyboards there, as this may be one for the 5.09 updates. (The Dutch (although their updates aren't always the same as the UK's so can't really be used to compare) have removed what they call the 'flo' keyboard) see images below for what I think may be the 'flo' keyboard
The small keyboard symbols are no longer there on the 5.09 update. It seems very trivial if that's all there is for this update. I suspect there must be more somewhere under the hood.