Help: Flash uploader not working

Hello All,

Our Flash uploader has stopped working on one of our sites and we can now only upload one media item at a time (real pain)!!

We had this problem once before and fixed it after a very long arduous manual replacement of files using FTP.

Looked up various similar postings in forums but none seem to have a fix for this, or they have been shut down without conclusion?

Can anyone advise please?