So what happens when you zoom in and out using the mouse wheel or the slider on the top left? Do the tiles display ok. What basemap are you using? are there any errors that appear in the console for your web browser?
What code are you using to zoom out to the full extent?
I saw this behavior when the scales of the cache don't match if you have several caches.
The JS API (unlike Silverlight) see in full extent that there is no scale and it fail to draw.
suggestions:
1. Match the scales of the caches.
2. Add a scale that fits the full extent.
Maybe I helped...
Oren