Patch 1.4.5x-1.4.5 not recognizing directory

[cjmpe]

I'm having trouble applying the 1.4.x to 1.4.5 patch to my Win64 install of KSP.  When I run it and point it to the install directory it fails saying "Please select a valid Kerbal Space Program folder".  I've still got the 1.4.x to 1.4.3 patch and it recognises the directory and tells me that KSP is already patched to 1.4.3 so I think the directory is valid.  Any suggestions would be appreciated...

[KerbolExplorer]

If you have steam try veryfing file integrety

[cjmpe]

Thanks for the advice.  I'm actually not using Steam for KSP.  I've been playing since 2013 and through inertia I've just kept on with the KSP site. 

Anyway, I went back to the KSP store and re-downloaded - the install worked correctly this time.  Very strange - I don't think I've ever seen an installer corrupted by a download actually start to function...