.Net Framework 4.6 Install results in error "%1 is not a valid win32 application"

I'm trying to install VisualStudio 2015RC and it fails with the following error "Microsoft .NET Framework 4.6RC %1 is not a valid Win32 application".

I've tried to just install the update to the .net framework and it fails with the same error. I'm running windows 8.1 with all updates installed. VS2013 is currently installed and VS2015 was installed and uninstalled in the past.

I've been trying to get VS2015 reinstalled for ages and I'm having zero luck - I've found references to that error but none seem to apply to this case. Does anyone have any ideas how to fix this, or how to dig in further to find a cause?

Ran the standalone installer again... here is the end of the log file

Action: Performing actions on all Items
Restart Manager: Detecting applications holding files in use.
RmShutdown failed with error: 351
RmShutdown failed with error: 351
Restart Manager complete
Action: Performing Action on Exe at C:\8d97d54073181c07907aaea600df\SetupUtility.exe
Exe (C:\8d97d54073181c07907aaea600df\SetupUtility.exe) succeeded.
Exe Log File: dd_SetupUtility.txt
Action complete
Action: Performing Action on Exe at C:\8d97d54073181c07907aaea600df\SetupUtility.exe
Exe (C:\8d97d54073181c07907aaea600df\SetupUtility.exe) succeeded.
Exe Log File: dd_SetupUtility.txt
Action complete
Action: Performing Action on Exe at C:\8d97d54073181c07907aaea600df\x64-Windows8.1-KB3033095-x64.cab
Exe (C:\8d97d54073181c07907aaea600df\x64-Windows8.1-KB3033095-x64.cab) failed with 0xc1 - (null).
PerformOperation on exe returned exit code 193 (translates to HRESULT = 0xc1)
Action complete
OnFailureBehavior for this item is to Rollback.
Action: Performing actions on all Items
Action complete
Action complete
Final Result: Installation failed with error code: (0x000000C1) (Elapsed time: 0 00:02:03).

The error led me to this post: https://social.msdn.microsoft.com/Forums/vstudio/en-US/ae4eaa00-3043-4e69-9b62-512da1a89f55/net-framework-4-installation-failed-with-1-is-not-a-valid-win32-application?forum=netfxsetup but so far the steps have not worked for me.

Maybe it is a bug with the RC version of .net Framework 4.6. Try to install the RTM version from .net 4.6 and the VS2015.