wonder if you can help...have taken photos off my mobile and put on my computer, i put them on a usb stick then tried to transfer onto an apple mac. the pictures came up as the thunbnails but wouldnt come up as actual pictures when i clicked on it...hope that made sense!
Although I'm a bit of computer geek, I cannot claim to be expert on Macs (I bought a s/h iMac G3, mostly to store my music MP3s on as it had a reasonable size HD, though screen is faulty and only displays in blue).
Does the Mac you are using have a browser like Firefox on it? Only ask, as you may be able to check if the file opens properly by dragging from folder onto FF.
If I see no other comments from Mac users, will check with a friend (though not heard anything from him recently so he and his family may be away on hols).
Macs seem to hold two items for files, one a sort of 'information' store, which in your case won't be present on the USB stick, as files came from a PC.