no thumbnails or preview on remote images

I can´t see any thumbnails or images even in the preview window on the remote side.
The image buffer size is high enough and I tried it on different remote directories.
Use Windows 8 X64 with the latest SFTP Version.
Any hints?
Thank you very much.
btw. How could I upload images here into my profile?

As it turned out the Windows registry on the customer's computer got corrupted and the problem was unrelated to SmartFTP.