Has anyone had this sort of trouble with scanning?

I'm trying to scan PDF documents and save them to Dropbox. It was working fine for a while and suddenly it stopped appearing in Dropbox. The Scan Result shows the title of the document, but no content. I've restarted my imac and that made no difference. I've tried on two separate scanners as well, but the results were the same. So I'm thinking it must have something to do with Image Capture. Does anyone have any suggestions?