We've been discussing this for weeks !
Some things seemed to have worked for other members, e.g. downloading Firefox and then Reader worked ok, another member paid Microsoft approx $60 to open a new account to rectify the problem, others just downloaded different free readers from cnet downloads.
Essentially it seems to me nobody knows the cause of the problem and if Adobe knows they are not telling.
There has been some really helpful posts on the problem so you are not alone !!
Hope you find an answer !
Since you mention AdbeRdr940_en_US.msi I assume that you are on Windows; what version?
Use the Windows Installer Cleanup Utility (http://majorgeeks.com/Windows_Installer_CleanUp_Utility_d4459.html) to remove the corrupted Adobe Reader; download, install, then run it.
I can not guarantee that the same thing will not happen again if you reinstall Adobe Reader, so in that case an alternate PDF viewer may be better in your case. Some suggestions:
Another popular alternate PDF viewer is "Foxit Reader", but I cannot recommend it as it installs spyware on users' computers.
Thanks for suggestions ! Will give them a try and see what happens !