I actually managed to get it to run on my MacBook with Snow Leopard in CrossOver Games 8.0.0, but it's a whole process.
What OS and CrossOver Games version are you using?
Here's what I did:
1) In CrossOver Games 8.0.0, I created a bottle with IE6 ( using the instructions in the Telltale trick on the tips & tricks page for Tales of Monkey Island at http://www.codeweavers.com/compatibility/browse/name/?app_id=5814;tips=1 ) and installed the game in it.
2) I installed CrossOver Games 7.2.2 on my computer (in a different folder than the one in which I have 8.0.0) and got it to run following the instructions on the following page: http://www.codeweavers.com/support/wiki/CXOffice7underSnow
3) I launched the bottle for the game in CrossOver Games 7.2.2 and unlocked the game via serial number, as all my attempts to log into my Telltale account from the launcher were unsuccessful.
In order to locate the box in which to enter the serial number, you first have to click (semi-) randomly in the middle of the right half of the launcher until two boxes appear asking for your login name and password (clicking randomly may lead you to a screen offering you to buy one episode or the whole season; just click on the button in the bottom-left corner to come back to the main screen).
Then, you have to click right above those boxes until a single box appears requesting your serial number.
Enter the serial number and click on the button (which might have just disappeared) just underneath the right end of the box and the game will unlock.
After this, the game should in CrossOver Games 7.2.2 and 8.0.0 (it does for me!).
Good luck!