Many thanks for your help, we ended up taking the bold step and dropped the database and did a complete re install of Photopost. Most of the site seems to be running fine now and I am absolutely delighted with it, I do still have one very small hiccup.
There appears to be an issue with the crossover between the Photopost software and the PHPBB3 software. If a member is logged into the gallery and clicks the "Forum" link they are registered on the forum as active and logged in users. However when they attempt to post they are asked to re login and are automatically forwarded to the forum front page logged out. It seems to be some kind of loop.
However if a member is NOT logged into the PHotopost gallery and logs directly into the forum they can post.
Please advise what might be the cause
Many thanks Helen