Permission problems Team Foundation Server - Build Agent

I am running a team foundation server on my virtual server. So far source control and everything else works as intended, but i have a problem when i wanna use the build agents to run automated builds on each check in.

What i did so far:

1. I create a user (called BuildMan) on my server and added it to a new user group. This user group gets execution and reading permissions for Visual Studio's folder and the build folder.
2. I added the user to the IIS_USER permission group as they have read/execute access to the build tools in the .NET framework folder in C:\Windows.

When i run a build everything works fine until i get the following error:

C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Microsoft.CSharp.targets (316): "Csc.exe" wurde mit dem Code -1073741502 beendet.

In english this means Csc ended with the code 0xC0000142 which means STATUS_DLL_INIT_FAILED. Im not sure, but i think this could be because it lacks permissions? If not, what could be my problem?

Try making that user a Local Admin and try again. That will at least confirm if it's permissions or something else.