If you upgraded to iOS 7 on your iPhone, iPad or iPod Touch and you are trying to use the YouTube voice search feature on the YouTube App, you are currently out of luck.
Every time you try to perform a voice search via the app, the app crashes.
A YouTube Help thread has several complaints with confirmation from a YouTube/Google representative.
YouTube’s Jennie said:
There is no ETA for a fix, but I suspect we should see one in the next few days.
Forum discussion at YouTube Help.