Well I uploaded the changed files and the following has happened:-
1) The Flash uploader says "Your file has been sucessfully processed" but no photo appears in the gallery.
2) If I turn off the Flash uploader then the old-style upload system refuses to work - either hangs (on 1 small file) or the message "Internet Explorer cannot display the web page" appears
I have deleted all old files, templates and
js scripts (except config of course), uploaded all new ones from the latest build and still have the same problems.
I have had to switch off the upload facility until this can be resolved. The site was working fine (without Flash 10 but with old style upload / Flash 9 etc) until the new files were uploaded this morning.