Your data works fine for me. I forgot to mention these need GDAL 1.7 and above, so that could be an issue if yours is 1.6.x:

13 14 googlemaps.html openlayers.html tilemapresource.xml

./13:
4698 4699

./13/4698:
5836.png 5837.png

./13/4699:
5836.png 5837.png

./14:
9396 9397 9398

./14/9396:
11673.png 11674.png 11675.png

./14/9397:
11673.png 11674.png 11675.png

./14/9398:
11673.png 11674.png 11675.png