I had a similar problem in Windows 7. I just went directly to the game installation folder and found the MonkeyIsland101.exe and launched it from there and it worked. Weird!
Although it may have been the other things I did first that fixed it -
Uninstall the game
Install the latest Direct X from here -
Reinstall the game UNCHECKING the direct X check and update.
Then go directly to C:\Program Files\Telltale Games\Tales of Monkey Island\Launch of the Screaming Narwhal\ and double click MonkeyIsland101.exe
That's what worked for me anyway.