It is simply the model taking time to load into the plug-in that is causing the problem. I have tested it in a number of browsers on a few OSs and the behaviour is the same in all cases.
The reason it works on subsequent page reloads is that the plug-in is caching the data so it isn't actually fetching the data a second time.
The zooming out, zooming in isn't doing anything to load the model any faster - it is simply passing the time until it loads.
On every test I have done the model always loads - but can take between 2 and 10 seconds to display...
There isn't a great deal you can do about this other than to try and optimise the .dae and image file within your KMZ archive to reduce the file size. This will make the model load and display faster than it currently does.