Right Click Menu Not Appearing

Hello,

Strange issue. I've tried searching both on here and online and not found a working resolution.

I have been working on a spreadsheet for a few hours. Previously, when I right clicked a cell I could insert a comment from the menu. However, when I right click now the menu does not appear. At the same time the menu stopped appearing the Formula Bar also disappeared. I have closed and reopened the spreadsheet and also rebooted my laptop. All to no avail (although the formula bar has reappeared!).

Any suggestions? I'm using Excel 2010, by the way...

Thanks,

John.

EDIT: Right click works in every other application - it's not a broken mouse as a colleague helpfully suggested!

have you closed Excel & re-opened the workbook or a new workbook?