I just resolved this exact problem. The issue with mine was that when wordpress and this plugin were updated, the image paths were switched with what they should be.
For example: I originally had them all as http://*Your URL*/wp-content/uploads/2012/06/*image file*
When I checked they had been switched to: http://*Your URL*/wp-content/plugins/image-horizontal-reel-scroll-slideshow/images/*image file*
You can check this by going to Settings > Image horizontal reel scroll slideshow > "Go To - Image Management" > Edit for one of your files. Your file path will be on the top bar, see if it has changed. You can either manually change all of the file paths by using edit or move your files in your FTP to the new path (this way is much faster IMO)
Also the code that adk2012 used for the V8.0 is absolutely correct.
I will paste mine so you can see another example but it is essentially the same...
[ihrss-gallery type="gallery1" w="600" h="85" speed="2" bgcolor="#FFFFFF" gap="1" random="no"]
Hopefully this is the problem with yours as well.