Navigation bar/sub pages error

I recently set up the Adelle theme on my website http://happyhillpups.com and I have had several people contact me to say that when they mouse over the Our Breeds tab in the navigation bar, there is no drop down menu, or it is there but they cannot select the subpages. One person said they tried it with Chrome and Safari on their iPad and it didn’t work … another person tried it on a computer and iPad (I’m not sure which browser) and sometimes it worked, sometimes it didn’t. I’m not having any trouble at all, so I’m not sure how to fix what I can’t reproduce! Any suggestions would be greatly appreciated.