What's the problem?

I downloaded Reader 11.0.10 (I previously had an older version that worked just fine).  Now I can't open .pdf files;  I have two recent .pdf files received after the download of 11.0 (both from sources that had previously sent .pdf files that I could open), and they won't open.  When I clk on them, the "circle" goes around for a while, then it stops and the files don't open.  I tried Adobe's little "Help" page, but no help, so Help!!

Thanks, Bob