You could try uninstalling and reinstalling it again but
remembering to restart your computer in between. (That restart is certainly necessary for problems with other Adobe software, such as Flash Player, so it might well apply here).
However, as Tuvok indicates, there's no need to use the slow, bloated software offered by Adode anyway. (Adobe invented the pdf format but others have vastly improved upon its implementation since then). As Tuvok indicates, Foxit is the most popular alternative and widely recommended. However this is what I use (and can thoroughly recommend):
http://blog.kowalczyk.info/software/sumatrapdf/free-pdf-reader.html
(Lousy website but great software!)