DLL stops when using nidaqmx function

[HHeyen]

Hello,

I'm trying to build a new dll using daqmx.
When I use examples creating an exe everything works fine. But when I copy the source to a DLL the code won't be executed.

I'm using
MSVC  6.0
DAQmx 8.6
Using MFC

example code: (I got this out of a forum entry)
    #include <NIDAQmx.h>

    #pragma comment( lib, "NIDAQmx.lib" )

...
void CNIDLL::CheckDevice()
{
        int buffersize,n=1;
        //Buffer size datatypes
        int devicetype_buffersize;
        int devicesernum_buffersize;

        //Device Info variable initialization
        char* devicenames= NULL;
        int devicesernum;
        devicenames=(char*)malloc(buffersize);
        //devicenames = (char*)malloc(devicenames, sizeof(char)*buffersize);
        //Get the string of devicenames in the computer
       //Here the compiler will stop in debug mode
        DAQmxGetSystemInfoAttribute(DAQmx_Sys_DevNames,devicenames,buffersize);
        DAQmxGetDevProductCategory("Dev1",&infoValue2);
        DAQmxGetDevProductType("Dev1", &s[0], 512);
}


Maybe I've to include something?

Regards
Helmut