I'm using filezilla.
I found this morning the folder gallery/images/medium on the test forum contains only index.htm and no image files.
This same folder on my live site and in my backups contains 421MB and 1274 files.
I tried using fireftp ( a addon to Firefox) and same problem.
I think this must be where the problem lies but why.
While uploading folder "medium" to the gallery/images directory on the test site using fireftp I refreshed the folder contents in filezilla and it showed an increasing number of files and MB's but after completion of the upload all that's left is index.htm
Now for some reason the server has blocked me temporarily due to "suspicious activity"