But it seems ridiculous that to output a file, you need to do that.

Try outputting to

C:\ProgramData\YourProgramsName\somefile.json

or

C:\Users\YourUserName\AppData\Local\YourProgramsName\somefile.json

At a guess, you've corrupted either your visual studio install or your antivirus.

Given that the C runtime on Windows is tied to versions of Visual Studio, it's quite possible that the C runtime specifically is corrupted. Or infected. Might be worth attempting to download and reinstall the runtime: http://www.microsoft.com/en-us/download/details.aspx?id=40784

Have you tried sending your program to someone else who also runs avast to see if their av also flags up the files as bad?

I did some reading up on avast and it seems it has an expert "hardened mode" that increases the aggressiveness of the heuristic engine.

This has to be manually enabled by the user. Did you enable this at any point by chance?

Get someone else to compile your code using Visual Studio 2013 (CE) and send the binary to you.

if need be i can send you a console mode 32 bit PE executable compiled with VS2012 express that writes a test text file to the current directory. then you'll have a known good exe, and can narrow it down to c runtime, UAC, or Avast. BTW, i think i've run avast in hardened mode with no problem before.

also, any folder under users or program files could potentially have UAC issues. testing using those folders is probably a waste of time until you find the problem. once you find the problem, then you can go back and get it working under those folders again.

Redownloaded VS and the Redistributables to no effect

what directory and file name did you try this time?

do you need me to create a new console project, and send you a test exe, source, solution file, etc?

the exe would test your C runtime, AV, and UAC. the project files would test your compiler install.

Mobile Developer at PawPrint Games ltd.
(Not "mobile" as in I move around a lot, but as in phones, mobile phone developer)
(Although I am mobile. no, not as in a babies mobile, I move from place to place)
(Not "place" as in fish, but location.)

sounds like Mr Kimball from Green Acres - well, not exactly like him - he usually talked about crops, not phones, unless it was a phonecrop - or was it a cropphone? Anyway - good luck fishing for your mobile baby! <g>.