Reassociating QuickLook file associations
It appears this is a Dropbox issue. While I had raised a question on Twitter, thanks to @szabolcs for creating a forum post, where others have chimed into.
Remove the /Applications/Dropbox.app/Contents/Library/QuickLook/DropboxQL.qlgenerator file.
@user1155120 was spot on; the beta version should be unchecked on the dropbox.com site, to prevent getting unstable updates. Download a new copy (v3.14.7 as of the time of this writing in 2016-03-02) and reinstall.