Powergallery Fixed - Thanks
Thanks for great support and fixing the code.
Webassist fixed the problem and telephoned to explain what had happened.
When I edited the PG_CachedResize_Image.php file, the code had been 'corrupted' by my Web Editing software (DW cs5 or Expression Web) something to do with the Byte-order Mark (BOM) option inserting extra code when editing PHP. In future, when editing PHP files I need to ensure that it was turned off