Thing is, I already have the same books on another Sony ereader and I'm not having any trouble [touch wood] viewing them on my computer in Calibre or on that reader.
I cant' believe it, I was working my way through sending you a detailed explanation of what was happening and second time round this morning - it all started working as it should. [Wouldn't do it for me yesterday when I needed it though]
Honest, there really was a problem but it seems to have disappeared!!! I will add, the strange symbol [small grey in the middles with red square around it] beside the epub is still there, but doesn't seem to affect the process now.
Something strange happened, but I can live with that for now.
Thank you so much for your input and very quick response.
Cheers