Updated to VS2013, Debug builds now broken

I installed VS2013 Community Update 4 with the intention of using shared projects. Since installing it, however, I’m now getting this error whenever I attempt to compile a debug version of the game, in both VS2012 and VS2013:

Error 1 The processor architecture of the project being built “Any CPU” is not supported by the referenced SDK “Microsoft.VCLibs, Version=11.0”. Please consider changing the targeted processor architecture of your project (in Visual Studio this can be done through the Configuration Manager) to one of the architectures supported by the SDK: “x86, x64, ARM”.

I’ve checked and rechecked this, and every project in the Debug configuration targets x86, just as in the Release configuration. Release builds and runs just fine.

Any idea what could be causing this?