ERROR : attempt to read or write protected memory this is often an indicating that other memory is corrupt

HI, 
when I run a visual application 2010 I get this error in try catch as function call test , this function get data from some dlls and C++ 

{"Attempt to read or write Protected Memory This is often an indicating that other memory is corrupt"} System.Exception {System.AccessViolationException}

I have tried to see Visual studio settings in  <pre>Tools menu ->Options -> Debugging -> General -> Uncheck this option "Suppress JIT optimization on module load"  AND and the same error still appears or   windows user as administrator  or over writing the camera manufacturer's dll

[DllImport("NVSSDK.dll", SetLastError = true)]
       public static extern Int32 NetClient_GetAlarmServer(Int32 _iLogonID, ref char[] _pcAlarmServer, ref Int32 _iServerPort );

char[] _pcAlarmServer = new char[16];
     Int32 _iServerPort = 0;

     try
     {
           // HERE IS THE ERROR
           int iRetx1 = NVSSDK.NetClient_GetAlarmServer(_ulLogonID,
                             ref _pcAlarmServer, ref _iServerPort);
     }
     catch (Exception ex)
     {

     }