My Bubble Sort, help

This sort seems to work the first time it is run, but if i run it a second time, it sorts the array in the opposite direction, and so on. Any ideas?

for (j = 0; j < i - 1; j++)
for (x = i - 1; x > j; --x)
if (VideoData[x-1].videocat < VideoData[x].videocat)
{
tmp = VideoData[x-1];
VideoData[x-1] = VideoData[x];
VideoData[x] = tmp;
}

// then print statements

Here's some code I wrote in java a while ago, the idea is the same for C and C++, except that i'm using vectors here.

Code:

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public int bubbleSort() {
  String temp;
  for(int i=0; i < current_size; i++) {
      for(int j=i+1; j < current_size; j++) {
        if(lessThan((String)data.elementAt(j),
            (String)data.elementAt(i))) {
            temp = (String)data.elementAt(j);
            data.setElementAt(data.elementAt(i), j);
            data.setElementAt(temp, i);
        }//end if
      }//end for
  }//end for
  return current_size;
}//end bubbleSort

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