what is error code -8003

We are trying to copy JPEG files from our desktop iMac to an empty 1GB flash drive (have tried several of those).

When we drag the file from the pictures folder and drop it onto the flash drive, we get this error:

The operation can’t be completed because an unexpected error occurred (error code -8003).

We have been unable to identify this error code and certainly do not understand the problem. We can open the image files in Preview. When we try to export them, or save them under another name, Preview churns, then goes back to its previous state without having opened a "Save As" window as it should.

When we use the duplicate function and try to work with a duplicate of the image file, Preview is unable to save those either. Tries for a while, then goes back to previous state. Further, I have to force quit to get out of Preview, because the duplicate is stuck open.