Nakedbabytoes - Thanks for the reply, it has nothing to do with my music files being moved or renamed, they are in exactly the same location as always, nothing changed. I have twice removed all the music from the iPad and then reloaded it and now there are no greyed out songs any longer. No doubt an ios5 bug. What is odd now is that the free space shown on itunes is 11gb which gives a total of 38gb hard drive on a 32gb ipad!!
The ipad itself gives the correct figure in its settings though.