An update on my experiences of this so far, plus the best solution so far in bold:
From what people have said here a factory reset solves the problem, but only termporarily.
A software update also seems to resolve it but again, only temporarily sadly. The issue reoccurs.
On my TV the factory reset isn't an something that I can do myself - the menu item for it is there but it is marked 'unavailavble'. An online chat to Samsung support (www.samsung.com) eventually lead to them doing a factory reset and this solved the problem. The whole thing took about 30 minutes - which would be fine if I only neede to do it once, but the problem was back the following day. :o(
Someone suggested this was a universal remote issue - but since the only remotes I have are the Samsung universal ones which came with the set and the problems are present with both of them this revelation hasn't helped much.
One poster said holding down the 'back' key until you had been taken all the way out of Now, then going back into it works. So far so good with this one - although early days and I can't swear yet that it works every time. Fingers crossed. If this continues to work it provides a fairly easy solution. You have to hold the 'back' key continually rather than keep pressing it lots of times. Thanks to the person who mentoned this - you may be the star of this thread.
Something I would say - don't waste time trying to work out what button is doing what on the remotes when this happens - there are some things that you can work out, like the up and down buttons take you you up and down the main menu. But this doesn't help you because you can't actually navigate anywhere else except up and down.
For people in the UK there is also a problem with My5 (pretty much most things freeze fairly quickly) and the holding the back button down thing doesn't make any difference to this one. The factory reset did solve it, but again only for 24 hours. I can live without My5 though.
Samsung if you are reading this - you need to sort this out uregently. Its been a known issue for a long while now - long enough for you to fix it and offer people a solution. I'm about to go oline and review my purchase and sadly because of this it's not going to be a great review.
