... You might want to check your file associations.
Haven't done anything, except installing Adobe Reader (from SBo) on one of the machines (the one I have now access to and the one the screenshot shows). The other one runs a still pristine
MLED; I'll check it later and will update this post if I find a difference
I have checked now and can confirm that the about:plugins page in Firefox is the same
on the pristine MLED 14.1 system.