Hi me again and I hope the last posting that you have from me on this subject.
Since my initial posting to this forum and the advice and help that you gave me I have had my hosting provider checking several of my servers for an answer to this problem.
For two weeks they tried to find it, and I finally gave them a rollocking and they then passed it to a senior engineer.
Today he/she came back with the answer.....
Carriage return before <?PHP on nearly all the admin pages, not on the public files but only on the admin pages.
Now, I know somebody at the start of all this told me that there mustn't be any spaces before the php tags and I did check, honestly. Either I checked the wrong set of files because I have the original download from Zen and also a backup copy of my site, so I looked again today and there they were!
Moral is - Check every single file in your working copy of admin for carriage returns.
I don't know how they got there and why only in admin and not in public?
Is the installer putting them in? Is my FTP programme putting them in? Whatever, I have done several virgin installs from more than one copy of Zencart and this problem is there from minute one!
Answer is I think to upload Zencart, install, download to desktop, open ALL admin files in good text editor [I use Crimson Editor] remove all the naughties and re-upload them to server.
I now have a reliable working admin and a very red face, there are some engineers in Manchester that I will REALLY need to buy coffee for!