This is an odd one, and chances are it’s very rare...

I noticed recently while working on a website, that the dropdown menu wasn't working. It took a click to get ‘focus’ before the drop down would occur – then I noticed it was happening with hovers, and anything else that requires the interface to be aware of the cursor hovering over it.

Naturally I assumed it was my CSS…after some wasted time, I discovered it was because my mouse was plugged in! It appears to be a conflict between the trackpad and the hardware mouse - but not all mice. It doesn't occur with a wireless Microsoft mouse, but does with the Saitek R.A.T 7.

It could be Steve Jobs punishing me from beyond the grave because I’m not using hallowed Apple hardware. I remedied the problem by installing the R.A.T control panel software.