excel change chart type drop down malfunction

The Change Chart Type drop-down list is not working on my Macbook. If I select a chart and then press the Change Chart Type menu button, the drop down list appears as expected, and the first approx. four items (e.g. Column, Line, Pie) I hover over highlight and show sub-items that I can select as expected. But if I continue to hover down the list, the following items do not highligt or show sub-items, and I cannot even click on them, and the previously well-behaved items are now also unresponsive. I can get around the problem by attacking the drop-down list from the side such that the item I want is one of the first I encounter, but it should not be necessary.

I just switched from Windows to this is a quite new Macbook, and I am surprised that such basic functionality seems to fail. Does anybody know an explanation and/or fix?