10.1.1 can be applied only on a 10.1 installation.
On the systems where you are seeing a failure, can you double check the existing Reader version?
Abhigyan, that's the impression I got from reading various blog posts. However, I've had multiple scenarios where I've attempted to load version 10.1.1 on top of version 10.1.0, and still gotten that error stating that I do not have a correct version. In addition, I have also seen this when attempting to apply 10.1.0 (previous patch) on top of version 10.0.0 or 10.0.1. It seems to be related to something that is getting dropped into the registry that the installation is seeing. It may only happen on boxes that previously had version 9.0, and on which version 10.0 was installed without first uninstalling 9.0, but I'm not sure if that is the exact scenario.
The way I was able to fix the problem I described above was to load the full exe of 10.1.1 (on top of 10.1.0), then uninstall Reader using Control Panel, and reload the SMS packages. I am able to successfully load base version 10.0.0 and then add on patch 10.1.1, without incrementing to 10.0.1 or 10.1.0 along the way.
yes, a fresh install of 10.1 or 10.1.1 should take care of the problem. As you have figured, the double dot quarterly releases of Reader X are cumulative, so need to apply only the latest one.