Try changing the font and then apply bold. Does it still crash? You may have corrupted font files.
Changing or disabling the default printer, perhaps temporarily, works, especially for network printers. e.g., install or use local rather than network printer. You could delete & reinstall the printer.
You could try updating printer drivers, or rolling back updated drivers if you don't lose other functionality doing so.
Another reason this might happen is if you have a customized toolbar (this includes add-ins). Find and delete the .xlb file. You'll have to re-do any customization from scratch, so maybe make notes on what customizations you might have.
Another thing you could try is a repair operation. In Add/remove programs, choose MS Office, click Change, select Repair.
This problem has been floating around for years and many versions of Office. Haven't seen a definitive solution yet.