In Windows 7 and Windows Server 2008 R2, Microsoft added a feature to the AppInit_DLLs mechanism. When the REG_DWORD RequireSignedAppInit_DLLs is set to 1, the DLLs to be loaded via AppInit_DLLs have to be signed.
You can find properly signed versions of LoadDLLViaAppInit here:
Nothing has changed to these DLLs, I’ve not changed the version number. I only set the FORCE_INTEGRITY flag and signed them.