The thing it avsViewer64 seems to work, if it opens the problem can't be missing dependencies of avsViewer64. 
So my guess is still that the problem is related with either:
a. access rights (or some virus scanner or similar interfering)
b. ffms2
-> did you test the different ffms2 versions?
So my guess is still that the problem is related with either:
a. access rights (or some virus scanner or similar interfering)
b. ffms2
-> did you test the different ffms2 versions?