Storyboard relies heavily on the 'Save for Web' engine within Photoshop to save your files so they look excellent and have a very small file size (fast loading on the web!) Sometimes settings within this 'Save for Web' window can get changed and it will effect the way Storyboard works; in this case saving HTML files instead of JPEG's of your Storyboards. Luckily this is an easy fix!
Open an image (any image at all) in Photoshop and then navigate to:
File - Save for Web and Devices
Once the Save for Web and Devices window pops open (it will show you the image and save settings on the right hand side) click save and you will see a 2nd dialog box asking you where you want to save the file...
... when you do, pay attention to the bottom - you want to make sure that this setting is "images only' (as shown in the provided screenshot) - just save the image to the desktop and your settings should be retained. Next time when you run Storyboard, it will be saving the images out and not html files.