Just wanted to verify if this is an issue on my end. I was going to work with Tilemaps and wanted to check out the test samples.
When I select TileMap test from the samples/tests menu I get: Uncaught TypeError: Cannot call method ‘getAttribute’ of undefined CCTMXXMLParser.js:534
I changed some file names for a couple of the ortho tests and it cleared up the problem.
I believe it was just orthogonal-test1.png and orthogonal-test2.png that were missing (though there was also a reference to ortho-test2.png, so I copied that one).
I think you should preload the images before use tilemap.