Recently, I changed to using Opera to download complete HTML websites (HTML + images) from the internet and save to various folders. Also, I backup my files periodically by using Thunar by copying to a USB Flash Drive. For some reason, Thunar will not copy these HTML files and folders to my USB Flash Drive (it copies everything else). I receive error messages such as, "Cannot copy [path . . . file] to [path . . . file] - invalid argument". Why is this? Would it be a configuration problem with Opera?
What file system is used on your flash drive? You could also try copying the files using something like MC - that may produce a clearer error message if it has a problem.
BTW, I gave up on Firefox. It would not open saved HTML files from Thunar (right click).
Strange. Works here without problems.