Hi, I encountered the same problem on Windows Phone 8 device. I'm using Cocos2d-X 2.2.3 and Visual Studio Express 2012 Update 4.
Basically, my app has several buttons allowing the user to tap simultaneously. On iOS, I have to add the line "[__glView setMultipleTouchEnabled:YES];" to enable multiple touch. On WP8, I didn't add any similar line to enable multiple touch. Though I can tap on several buttons (e.g., 3 buttons) simultaneously at the beginning, after some time the message "The touches is more than MAX_TOUCHES, nUnusedIndex = -1" is prompted and after that I can at most tap on 1 button (i.e., no multiple touch).
Any idea to solve the issue? Extra code is needed to enable multiple touch on WP8? Thx!