Fejl: Unbalanced stack

Hej eksperter

Jeg har fundet denne kode stump til at afspille en wav fil i min form:

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Runtime.InteropServices;

namespace Timer
{
    public class WAVSounds
    {
        [DllImport("WinMM.dll")]
        public static extern bool PlaySound(byte[] wfname, int fuSound);

        //  flag values for SoundFlags argument on PlaySound
        public int SND_SYNC = 0x0000;      // play synchronously (default)
        public int SND_ASYNC = 0x0001;      // play asynchronously
        public int SND_NODEFAULT = 0x0002;      // silence (!default) if sound not found
        public int SND_MEMORY = 0x0004;      // pszSound points to a memory file
        public int SND_LOOP = 0x0008;      // loop the sound until next sndPlaySound
        public int SND_NOSTOP = 0x0010;      // don't stop any currently playing sound

        public int SND_NOWAIT = 0x00002000; // don't wait if the driver is busy
        public int SND_ALIAS = 0x00010000; // name is a Registry alias
        public int SND_ALIAS_ID = 0x00110000; // alias is a predefined ID
        public int SND_FILENAME = 0x00020000; // name is file name
        public int SND_RESOURCE = 0x00040004; // name is resource name or atom
        public int SND_PURGE = 0x0040;    // purge non-static events for task
        public int SND_APPLICATION = 0x0080;    // look for application specific association

        public void Play(string wfname, int SoundFlags)
        {
            byte[] bname = new Byte[256];    //Max path length
            bname = System.Text.Encoding.ASCII.GetBytes(wfname);
            PlaySound(bname, SoundFlags);
        }

        public void StopPlay()
        {
            PlaySound(null, SND_PURGE);
        }
    }
}

og jeg kalder play med dette:

string file = "C:\\Documents and Settings\\Mikkel Sommer\\Skrivebord\\1234.wav";
WAVSounds ws = new WAVSounds();
ws.Play(file, ws.SND_ASYNC);

Men når jeg kører det får jeg fgl. fejl, og ingen lyd bliver spillet:

A call to PInvoke function 'Timer!Timer.WAVSounds::PlaySound' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature.

Det mest underlige er at hvis jeg indsætter et breakpoint ved PlaySound(bname, SoundFlags); og trykker f11 spilles lyden men ved f10 sker der ikke noget(som når jeg kører det uden breakpoint).

Håber der er nogen som kan hjælpe mig videre...