Finally got a temporary fix by using Chromium browser instead of Firefox.
I lay most of the blame with Adobe. Note that:
1) I woke up one morning to find that myspace no longer worked with Ubuntu Hardy (8.04) and Flash 9 on my laptop. I attempted to install Flash 10 as suggested and it failed even at this stage (with no upgrade of Ubuntu in mind).
2) I decided to upgrade in case Hardy was the problem - it was just a freak that Lucid LTS came online at exactly this time (or was it?)
3) You all know the upgrade fracas.
4) When I finally got Flash 10 working on Chromium, I found that on myspace adverts were appearing over the top of the player (and stopping it). Is this why they wanted to use Flash 10 - did it facilitate popup adverts? Was it released too soon to get this going?
I am not happy. Unfortunately I need myspace - as a folk club co-organiser I need to listen to a lot of material put there by intending (grossly underpaid) 'Guests' (as we call artists). I also listen a lot to BBC radio on the web for 'listen again' - currently it doesn't work on my Firefox despite being notionally useable with Flash 9. (But a clean install of Lucid on a cruddy old desktop in another room works fine with Firefox.)
I believe this is not off-topic - sorry if you disagree.