Problem displaying char with ASCII code 255

[paskuda]

I'm having that probably very stupid problem, yet I can't find an answer, so ...
My application has to make a hex dump of some buffer (read from binary file). I have a pointer to that buffer:

char *headerPtr;

To read it byte by byte I wrote a function

char header::getByteAtPos(int pos){
if( pos > hsize ) {
  return NULL;
  }
char ret = *(headerPtr + pos);
return ret;
}

As you see, first I check whether position is not outside the buffer, then I increment buffer pointer and read the char located at calculated position.

In the main() function I have following piece of code :

for(int i=0,w=0; i<X->size; i++, w++) {
  [cut unimportant formatting stuff]
  sp = X->getByteAtPos(i);
  printf("%02X ",sp);
 }

Everything works fine and dumped values are correct (I compared them with Hexplorer output unless returned char's ASCII code is 255. See the output yourself:

4D 5A 50 00 02 00 00    00 04 00 0F 00 FFFFFFFF FFFFFFFF 00

These FFFFFFFF fields should be displayed as FF. Everything else is correct. At first, I thought I'm doing something wrong with printf(), but using cout << hex << int(sp) produced the same.

Any ideas ?

Mike