Compiler or code error?

Here I have a function that sends a request to a server to delete a file. But, it always crashes on a certain line when compiled in debug mode and runs fine when compiled in release mode. Is this a compiler error? Here's my code:

Code:

void deleteFile(HWND hWnd)
{
     //Get a handle to the listbox control
     HWND lb = GetDlgItem(hWnd, IDC_REMOTEFILES); //lb = listbox

     //Get the index of the listbox item
     int index = SendMessage(lb, LB_GETCURSEL, 0, 0);

     //Get the length of the item and allocate a string for it
     int len = SendMessage(lb, LB_GETTEXTLEN, index, 0);
     char* fNameBuf = new char[len];
     unsigned char nameLen = SendMessage(lb, LB_GETTEXT, index, (LPARAM)fNameBuf);

     unsigned long msgLen = 1;
     msgLen += sizeof(nameLen);
     msgLen += nameLen;
     server->send(htonl(msgLen));

     server->send(ICV_OP_DELETE);
     server->send(nameLen);
     server->send(fNameBuf);

     unsigned char result;
     server->receive((char*)&result, 1);

     if(result == ICV_SR_ERR)
          MessageBox(hWnd, "File could not be deleted.", "Error", MB_OK);
     else if(result == ICV_SR_OK)
          MessageBox(hWnd, "File successfully deleted.", "Success", MB_OK);
     else
          MessageBox(hWnd, "Unknown protocol error.", "Error", MB_OK);

     MessageBox(hWnd, "Going to delete fNameBuf", "c", MB_OK);
     delete[] fNameBuf;
     MessageBox(hWnd, "fNameBuf deleted", "k", MB_OK);
}

It always crashes between the 2 last messageboxes, right after I click ok on the "Going to delete fNameBuf". The crash thing that pops up says:

Debug error!

Program: (...)

Damage: after Normal block (#22) at 0x00F10D90

(abort, retry, ignore)

Should I look to my code or my compiler for the problem? I really can't see anything wrong with the code, but I thought I'd ask just in case, since it's just about always my fault anyways

**EDIT**
Wasn't sure if this belonged on the c++, networking, or Windows board, but since the code involves Windows API I thought I'd put it under Windows... hope the mods don't mind.

Code:

 int len = SendMessage(lb, LB_GETTEXTLEN, index, 0);
char* fNameBuf = new char[len];

MSDN LB_GETTEXTLEN

The return value is the length of the string, in TCHARs, excluding the terminating null character.

You need +1.

Ok, thanks for all the help guys Guess I better be tracking that bounds overflow thinger down now

**EDIT**
Ahha... ahem... Oops, I forgot to add a "+1" for the null 0

**EDIT2**
Eep I didn't read wledge's post