I cannot run Lightroom, because it tells me it cannot find MSVCR100.DLL. I've researched this and found usggestions to down load the latest Visual Basic realease files frmo Microsoft. Did that. Still doesn't work. And a search of my computer confirms that I have the DLL.
This issue really appears to be because of an installation of iLivid at some point (a download manager, perhaps installed without your knowledge), corrupting libraries needed to run the 64 bit version of Lightroom. I found that the 32 bit version always worked so, if all else fails, just install the 32 bit version and run it. You probably won't notice the difference unless you are fooling with huge files and lots of other things running on on your computer.
I uninstalled iLivid and the 64 bit version of Lightroom, replaced the two files from Microsoft and reinstalled Lightroom 64 bit and the problem never returned.
If you are still facing the issue, download and install the MSVC 2010 Redistributable from http://www.microsoft.com/en-us/download/details.aspx?id=26999
Make sure that you pick the correct x64 / x86 version that corresponds with your system.