Excel Dialog box partly visible

[nmrosen]

When I right-click to either insert or format cells in my 2007 Excel running on a Win 8 PC 64 pro system I sometimes get only the top of the dialog box visible. Changing the color scheme does not help. Sometimes, I see a whole dialog box when I right click on a cell and sometimes I get only the top of the box. If I get only the top visible, and I keep trying sooner oir later the full box appears. The same thing happens with the dialog box to insert or remove a row or column. The problem appears sporatically, but it is very annoying and I'd love to get a fix. This never happened when I used earlier versions of WIndows.