Have the same issue using iPad. Additionally, if I click the forum tab to get the drop down menu before I can select one of the two options it automatically takes me to /forum. Only happens from iPad, not pc or iPhone.
Thank you to God for making me an Atheist - Ricky Gervais.
The menu effect is because the forum menuitem is a link in itself, rather than only a dropdown item.
I'm working to resolve this at the same time as some site menu restructuring. The strange layout will also be resolved then (or at least I'll try to).