Installation error: Can't initialize plug-ins directory

I’m trying to install Julia 0.6.2 from Download Julia on Windows 7, and get the following error:
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I have verified the installer MD5 checksum and tried installing after a reboot. My machine also has JuliaPro 0.6.2.1 installed, but I have no problem using the “vanilla” Julia alongside JuliaPro (using the same versions) on a different machine with Windows 10.