Hello,
We’ve updated to ELAN 3.3.0 on our Mac OS X Leopard machines in order to be able to pull in Praat text files. 
Do you have a document opened? In contrast to import of Toolbox or Transcriber etc. files, where always a new document is created, the Praat import adds tiers to an existing, open document.
So, if you create a new document picking the right audio file, you should be able to choose File -> Import -> Praat TextGrid File… and browse to the Praat file corresponding to the audio file.
Han
Yes, we did have a file open, and video media imported, but we discovered that we had it in the wrong format.