Existing images/download files not found when adding a new product

I have been using this version of Zen Cart v139d for a year or so without problems.
Starting from yesterday 28th June 2012 I find that when adding a new product, if I select an existing image file from the server
it is not found, if instead I upload the image this works fine.
In a similar problem, when using the attributes manager for a new virtual product, the existing download file is not found.
I have previously added many products without ever having this problem.

Any help with this will be appreciated.

I have fixed the problem.
It was caused by uploading the files directly from a cruzer memory stick.
I transfered the files to my desktop and uploaded into Zen Cart from there and
the problem disappeared.