I had this same problem when trying to compile a third party MFC dll using /clr.  After a few hours of frantic clicking around and much cursing, I finally figured out that the project itself was not using Run-Time Checks, but each file had that option set individually.  In other words, turning Run-Time Checks off for the project does not necessarily turn them off for each file.

Right click a code file in Solution Explorer and select the Properties.  Then go to "Code Generation" under the C\C++ node and check the "Basic Runtime Checks" property.  I'm betting it will indicate that Run-Time Checks are on for at least one of the files.

Hope that helps.

Hi,

I've noticed that the settings of each code file is stored in the
parent project settings file "YourProject.vcproj" in standard XML
format.

"Basic Runtime Checks" property appears like this in the .vcproj file

<VisualStudioProject>
   <Files>
       <Filter Name="Source Files" ...>
           <File RelativePath="YourCode1.cpp">
               <FileConfiguration
Name="Debug|Win32">
                   <Tool
                       .
                       .
                       BasicRuntimeChecks="3"
                       .
                       . />
               </FileConfiguration>
           </File>
           <File RelativePath="YourCode2.cpp">
               <FileConfiguration
Name="Debug|Win32">
                   <Tool
                       .
                       .
                       BasicRuntimeChecks="3"
                       .
                       . />
               </FileConfiguration>
           </File>
           .
           .
           .
       </Filter>
   </Files>
</VisualStudioProject>
The values are :
"0" : Default
"1" : /RTCs
"2" : /RTCu
"3" : /RTC1

The better thing to do is to delete the line {BasicRuntimeChecks="3"}
as the code will inherit from project defaults.

You may be able to make a script to do this automatically.
Hope it will help you.